Aortic occluder with associated filter and methods of use during cardiac surgery

ABSTRACT

A balloon arterial cannula and methods for filtering blood. The devices generally include a mesh for filtering blood flowing within a blood vessel, particularly within an artery such as the aorta, a structure adapted to open and close the mesh within the blood vessel, a means to actuate the structure, and a balloon occluder which typically includes a flexible material enclosing a chamber. The methods generally include the steps of introducing a mesh into a blood vessel to capture embolic material, adjusting the mesh, if necessary, during the course of filtration, inflating the balloon occluder to occlude the vessel upstream of the mesh, and thereafter deflating the balloon occluder and removing the mesh and the captured foreign matter from the blood vessel. Additionally, visualization techniques are used to ensure effective filtration.

This is a continuation of U.S. application Ser. No. 08/854,806, filedMay 12, 1997, which is a continuation-in-part of U.S. application Ser.No. 08/645,762, filed May 14, 1996, now abandoned. All of the aboveapplications are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to blood filter devices havingan associated balloon occluder for temporary placement in a bloodvessel, and more particularly to a cannula device, having an associatedblood filter and balloon occluder, for placement in a blood vessel tocarry blood to an artery from a bypass-oxygenator system and to captureembolic material in the vessel. The invention also relates to cathetershaving a balloon occluder and associated filter to capture embolicmaterial. More particularly, the invention relates to a blood filterdevice to be placed in the aorta during cardiac surgery, the devicefurther having a balloon occluder which, when deployed, reduces oreliminates the need for aortic cross-clamping. The present inventionalso relates to methods for temporarily filtering blood to capture andremove embolic material, and to methods for protecting a patient fromembolization which may be caused by the balloon occluder havingdislodged atheromatous material from the artery.

BACKGROUND OF THE INVENTION

Currently, the most common method of temporarily occluding the ascendingaorta during open heart surgery utilizes a mechanical cross clamp. Oncethe chest cavity has been opened, access to the heart and to theadjacent vessels is provided. The ascending aorta is partially dissectedfrom the surrounding tissue and exposed. Arterial and venous cannulasare inserted and sutured into place. The cannulas are connected to thecardiopulmonary bypass machine, and bypass blood oxygenation isestablished.

At this point, the heart must be arrested and isolated from the rest ofthe circulatory system. A mechanical cross clamp is positioned betweencardioplegia cannula and the aortic cannula and actuated. The aorta iscompletely collapsed at the clamp site, thus stopping flow of bloodbetween the coronary arteries and the innominate artery the oxygenatedbypass blood is shunted around the heart. Once the vessel occlusion hasbeen completed, cardioplegia solution is introduced through thecardioplegia cannula to arrest the heart. The surgeon may now proceedwith the desired operation.

Other less common means of occluding the aorta include percutaneousballoon catheter occlusion, direct aortic balloon catheter (Foley)occlusion, aortic balloon occluder cannula, and an inflating diaphragmoccluder (Hill--occlusion trocar). The percutaneous balloon catheter isinserted typically from the femoral artery feed through the descendingaorta, across the aortic arch into position in the ascending aorta. Oncein the ascending aorta, the balloon occluder is inflated and flowstopped.

As a simple replacement for the mechanical cross clamp, a Foley cathetermay be placed through an additional incision site near the standardcross clamp site. Once inserted, the Foley catheter balloon is inflatedand flow is stopped. Similarly, an aortic balloon occluder cannula isplaced directly into the aorta. This occluder cannula replaces thestandard aortic cannula by delivering the CPB blood back to the arterialcirculatory system. The occluder balloon is located on the cannulaproximal to CPB blood exit port on the cannula. It may also replace theneed for a cardioplegia cannula with an additional infusion portproximal to the occluder balloon. The occlusion trocar is described tooffer similar features as the aortic balloon occluder cannula and wouldbe used in place of the standard aortic cannula. However, it relies onan inflatable diaphragm to occlude the vessel.

The use of a balloon to occlude an artery has been disclosed by Gabbay,U.S. Pat. No. 5,330,451 (this and all other references cited herein areexpressly incorporated by reference as if fully set forth in theirentirety herein). The Gabbay device included a perfusion cannula havinga proximal balloon occluder and a distal intra-aortic balloon to divertblood to the carotid arteries. The Gabbay perfusion cannula is disclosedfor use during open heart surgery in order to prevent complicationsassociated therewith.

Moreover, Peters, U.S. Pat. No. 5,433,700, discusses a method forinducing cardioplegic arrest using an arterial balloon catheter toocclude the ascending aorta. The Peters method includes the steps ofmaintaining systemic circulation using peripheral cardiopulmonarybypass, venting the left side of the heart, and introducing acardioplegic agent into the coronary circulation. This procedure is saidto prepare the heart for a variety of surgical procedures. Disclosuresof similar endovascular occlusion catheters can be found in Machold etal., U.S. Pat. No. 5,458,574, Stevens, International Application No.PCT/US93/12323, and Stevens et al., International Application No.PCT/US94/12986.

There are a number of known devices designed to filter blood. The vastmajority of these devices are designed for permanent placement in veins,in order to trap emboli destined for the lungs. For example, Kimmell,Jr., U.S. Pat. No. 3,952,747, discloses the so-called Kimray-Greenfieldfilter. This is a permanent filter typically placed in the vena cavacomprising a plurality of convergent legs in a generally conical array,which are joined at their convergent ends to an apical hub. Each leg hasa bent hook at its end to impale the internal walls of the vena cava.

Cottenceau et al., U.S. Pat. No. 5,375,612, discloses a blood filterintended for implantation in a blood vessel, typically in the vena cava.This device comprises a zigzagged thread wound on itself and a centralstrainer section to retain blood clots. This strainer section comprisesa meshed net and may be made from a biologically absorbable material.This device is also provided with attachment means which penetrate intothe wall of the vessel.

Gunther et al., U.S. Pat. No. 5,329,942, discloses a method forfiltering blood in the venous system wherein a filter is positionedwithin a blood vessel beyond the distal end of a catheter by apositioning means guided through the catheter. The positioning means islocked to the catheter, and the catheter is anchored to the patient. Thefilter takes the form of a basket and is comprised of a plurality ofthin resilient wires. This filter can be repositioned within the vesselto avoid endothelialization within the vessel wall.

Similarly, Lefebvre, French Patent No. 2,567,405, discloses a bloodfilter for implantation by an endovenous route into the vena cava. Thefilter is present in the form of a cone, and the filtering means mayconsist of a flexible metallic grid, or a flexible synthetic or plasticgrid, or a weave of synthetic filaments, or a non-degradable or possiblybiodegradable textile cloth. In order to hold the filter within thevein, this device includes flexible rods which are sharpened so thatthey may easily penetrate into the inner wall of the vena cava.

There are various problems associated with permanent filters. Forexample, when a filter remains in contact with the inner wall of thevena cava for a substantial period of time, endothelialization takesplace and the filter will subsequently become attached to the vena cava.This endothelialization may cause further occlusion of the vessel,thereby contributing to the problem the filter was intended to solve.Except for the Gunther device, these prior art filters do not addressthis problem.

A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No.5,053,008. This device treats emboli in the pulmonary artery which,despite its name, is in fact a vein. The Bajaj device is an intracardiaccatheter for temporary placement in the pulmonary trunk of a patientpredisposed to pulmonary embolism because of hip surgery, stroke orcerebral hemorrhage, major trauma, major abdominal or pelvic surgery,neurosurgery, neoplasm, sepsis, cardiorespiratory failure orimmobilization.

The Bajaj device includes an umbrella made from meshwork which trapsvenous emboli before they reach the lungs. This device can also lyseemboli with a thrombolytic agent such as tissue plasminogen activator(TPA), destroy emboli with high velocity ultrasound energy, and removeemboli by vacuum suction through the lumen of the catheter. This very,complex device is designed for venous filtration and is difficult tojustify when good alternative treatments exist.

There are very few intravascular devices designed for arterial use. Afilter that functions not only in veins, but also in arteries mustaddress additional concerns because of the hemodynamic differencesbetween arteries and veins. Arteries are much more flexible and elasticthan veins and, in the arteries, blood flow is pulsatile with largepressure variations between systolic and diastolic flow. These pressurevariations cause the artery walls to expand and contract. Blood flowrates in the arteries vary from about 1 to about 5 L/min.

Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial device. Thisdevice includes a catheter that has a strainer device at its distal end.This device is normally used in conjunction with non-surgicalangioplastic treatment. This device is inserted into the vesseldownstream from the treatment site and, after the treatment, thestrainer is collapsed around the captured emboli, and the strainer andemboli are removed from the body. The Ginsburg device could notwithstand flow rates of 5 L/min. It is designed for only small arteriesand therefore could not capture emboli destined for all parts of thebody. For example, it would not catch emboli going to the brain.

Ing. Walter Hengst GmbH & Co, German Patent DE 34 17 738, disclosesanother filter which may be used in the arteries of persons with a riskof embolism. This filter has an inherent tension which converts thefilter from the collapsed to the unfolded state, or it can be unfoldedby means of a folding linkage system. This folding linkage systemcomprises a plurality of folding arms spaced in parallel rows along thelongitudinal axis of the conical filter (roughly similar to branches ona tree). The folding arms may be provided with small barbs at theirprojecting ends intended to penetrate the wall of the blood vessel toimprove the hold of the filter within the vessel.

Moreover, da Silva, Brazil Patent Application No. PI9301980A, discussesan arterial filter for use during certain heart operations where theleft chamber of the heart is opened. The filter in this case is used tocollect air bubbles in addition to formed particles such as plateletfibrin clots not removed on cleaning the surgical site.

Each of the existing methods of blocking aortic blood flow carries withit some undesired aspects. The mechanical cross clamp offers simplicityand reliably consistent operation. However, the physical clamping actionon the vessel has been linked to may adverse body responses. Barbut etal. noted the majority of embolic events (release) is associated withthe actuation and release of the cross clamp during coronary bypassgraph surgery. The clamping action may be responsible for breaking upand freeing atherosclerotic buildup on the vessel walls. In addition,the potential for vascular damage, like aortic dissections, may alsoincur during the clamp application.

The percutaneous balloon catheter occluder has a distinct drawback inthat it must be placed with visionary assistance. Fluoroscopy istypically used to position the device in the aorta. This added equipmentis not always readily available in the surgical suite. In addition, thecatheter placement up to the aorta may also create additional vasculartrauma and emboli generation.

The use of a Foley catheter to occlude the aorta requires an additionalincision site to place the device. This extra cut is an additionalinsult site and requires sutures to close. Generation of emboli and thepotential of aortic dissection directly associated with just theincision may potentially outweigh the benefits of using the balloonocclusion technique.

The aortic balloon occluder cannula addresses many of the deficienciesof the previous devices. Placement is easy to visualize and no extracuts are required. With the cardioplegia port included, this designoffers a complete package while potentially reducing the number ofincision sites and removing the need for the potentially traumatic crossclamp. However, this "all-in-one" design possesses several deficiencies.First, there is one inherent drawback with using a balloon to occlude avessel. Balloons are always susceptible to failure (e.g., popping,leaking). In addition, the cannula has a limited placement region. Itmust be inserted sufficiently proximal to the innominate artery to allowroom for occlusion balloon to seat within the vessel and not occlude orblock the innominate artery. This cannula design has at least twocritical functions (three with the cardioplegia port). A balloon failuremeans either replacing the cannula (stopping the CPB and cardioplegia),or immediately placing the cross clamp and inserting a cardioplegiacannula. Life support, occlusion, and cardioplegia depend on one device.This situation is less than optimal. The risks associated to a failureare multiplied when one device is used or more than one criticaloperation.

A need exists for an arterial cannula having both a balloon occluder,which reduces or eliminates the need for aortic cross-clamping, a majorcontributor to atheromatous embolization, and an associated filter whichcaptures any embolic material dislodged during balloon occlusion.Existing devices are inadequate for this purpose.

SUMMARY OF THE INVENTION

The present invention relates to arterial medical devices, andparticularly cannulas and catheters having an occlusion balloon andoptionally a blood filter device, and to methods of using the devicesduring cardiac surgery. The devices of the present invention may beadapted to filter embolic material from the blood. Embolic material orforeign matter is any constituent of blood, including gaseous materialand particulate matter, which may cause complications in the body ifallowed to travel freely in the bloodstream. This matter includes but isnot limited to atheromatous fragments, fat, platelets, fibrin, clots, orgaseous material.

In one embodiment, the device includes a blood cannula having a balloonoccluder at a distal region of the blood cannula. In another embodiment,the device includes an intravascular catheter having a balloon occluderat a distal region of the catheter. The balloon occluder may consist ofa flexible material surrounding a chamber which is expandable between adeflated, contracted condition and an inflated, enlarged condition. Theballoon occluder may be circumferentially disposed about a distal regionof the catheter or blood cannula, or may be attached to the catheter orblood cannula at a specific radial position about the distal region ofthe catheter or blood cannula. The balloon occluder, when in thecontracted condition, is closely associated with the distal region ofthe catheter or blood cannula, while the balloon occluder expands uponinflation to occupy an area which may occlude blood flowing within anartery.

In another embodiment, the blood cannula or catheter will furtherinclude filtration means disposed about the distal region of thecatheter or blood cannula. Several designs for blood filtration cannulasare disclosed in Barbut et al., U.S. application Ser. No. 08/553,137,filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223,filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No.08/584,759, filed Jan. 9, 1996, and Barbut et al., U.S. application Ser.No. 08/640,015, filed on Apr. 30, 1996, and Barbut et al., U.S.application Ser. No. 08/842,727, filed Apr. 16, 1997, and the contentsof each of these prior applications are incorporated herein by referencein their entirety. Thus, in one embodiment, the balloon aortic cannulaas disclosed herein will include a filtration means having an expandablemember, such as an inflation seal, disposed about the distal end of theblood cannula, which is expandable between a deflated, contractedcondition and an inflated, enlarged condition. The filtration means willfurther include a mesh having an edge attached to the expansion means.The mesh may optionally include a second edge which is closelyassociated with the outer surface of the blood cannula, or the mesh maybe continuous and unbroken at its distal region. The filtration meanswill generally be disposed about the distal end of the blood cannula andthe balloon occluder at a region proximal of the mesh, so that theballoon occluder expands upon inflation to substantially occlude anartery upstream of the mesh. For those embodiments using anintravascular catheter, the balloon occluder is typically upstream ofthe filtration means, or with reference to the catheter, distal thefiltration means.

In another embodiment, a cannula with filtration means further includesa blood flow diffuser. The blood flow diffuser may be located inside oroutside of the blood cannula. In both the intra-cannula andextra-cannula diffuser embodiments, the flow diffuser can be locatedeither proximal or distal to the filtration means. The diffuser may besimilarly used for intravascular catheter embodiments of the device.

In another embodiment, a cannula with attached filtration means includesa sleeve which, when unrolled, captures the filtration means therebyclosely securing the filter components against the cannula wall duringinsertion and retraction. The sleeve may be similarly used forintravascular catheter embodiments of the device. In another embodiment,a cannula is made of an elastomeric material which collapses along partof the cannula length so as to absorb the filtration means duringcannula insertion and retraction.

In an alternate embodiment, a blood cannula includes a conduit toprovide a solution, such as cardioplegia solution, to the heart side ofan aortic balloon occluder while providing oxygenated blood into thearterial circulation of the systemic side of the occluder.

The methods of the present invention include protecting a patient fromembolization during cardiac surgery by using a balloon aortic cannula asdescribed above or other intravascular or intra-arterial procedureresulting in distal embolization. The distal end of the arterial cannulais inserted into a patient's aorta while the filtration and expansionmeans is in the contracted condition. The expansion means, includingassociated mesh, is inflated to expand and thereby achieve contact withthe inner wall of the artery, preferably the aorta. Once the filtrationmeans are in place and deployed, the balloon occluder is activated byinflating to occlude the artery, preferably the aorta, in a regionupstream of the mesh. In other embodiments, the balloon occluder may beinflated before the expansion means is inflated. During balloonocclusion, certain embolic material may be dislodged from the artery,and thereafter captured by the deployed filtration system. The cannulais used to supply blood to the aorta from a bypass-oxygenator machine. Asurgical procedure may then be performed on the heart, aorta, orvasculature upstream of the deployed filtration system. During thisprocedure, further embolic material may be dislodged and enter thecirculation, and thereafter be captured by the deployed filtration mesh.After the surgery is performed, the balloon occluder is deflated, andfurther embolic material may be dislodged and captured by the filtrationsystem. The expansion means of the filtration system is then contractedby deflating to resume a small shape, and the arterial cannula withcaptured embolic material is removed from the aorta.

In a preferred method, balloon occlusion occurs, and blood is filteredduring cardiac surgery, in particular during cardiac bypass surgery, toprotect a patient from embolization. In this method, the mesh ispositioned in the aorta where it filters blood before it reaches thecarotid arteries, brachiocephalic trunk, and left subclavian artery.

The present invention was developed, in part, in view of a recognitionof the occurrence of embolization during cardiac surgery. Emboli arefrequently detected in cardiac surgery patients and have been found toaccount for neurologic, cardiac and other systemic complications.Specifically, embolization appears to contribute significantly toproblems such as strokes, lengthy hospital stays and, in some cases,death. Of the patients undergoing cardiac surgery, 5-10% experiencestrokes and 30% become cognitively impaired. In addition, it has beenrecognized that embolization is often the result of procedures performedon blood vessels such as incising, clamping, and cannulation, whereinmechanical or other force is applied to the vessel. See, for example,Barbut et al., "Cerebral Emboli Detected During Bypass Surgery AreAssociated With Clamp Removal," Stroke 25(12):2398-2402 (1994), which isincorporated herein by reference in its entirety. These procedures arecommonly performed in many different types of surgery including cardiacsurgery, coronary artery surgery including coronary artery bypass graftsurgery, aneurysm repair surgery, angioplasty, atherectomy, andendarterectomy, including carotid endarterectomy. It has also beenrecognized that reintroducing blood into blood vessels with a cannula orcatheter during these procedures can dislodge plaque and otheremboli-creating materials as a result of blood impinging upon the vesselwall at high velocities. See, for example, Cosgrove et. al., LowVelocity Aortic Cannula, U.S. Pat. No. 5,354,288.

Finally, it has been found that the occurrence of embolization is morelikely in certain types of patients. For example, embolization occursmore frequently in elderly patients and in those patients who haveatheromatosis. In fact, atheromatous embolization, which is related toseverity of aortic atheromatosis, is the single most importantcontributing factor to perioperative neurologic morbidity in patientsundergoing cardiac surgery.

Embolic material, which has been detected at 2.88 mm in diameter, willgenerally range from 0.02 mm (20 μm) to 5 mm, and consists predominantlyof atheromatous fragments dislodged from the aortic wall and air bubblesintroduced during dissection, but also includes platelet aggregateswhich form during cardiac surgery. See Barbut et al., "Determination ofEmbolic Size and Volume of Embolization During Coronary Artery BypassSurgery Using Transesophageal Echocardiography," J. CardiothoracicAnesthesia (1996). These emboli enter either the cerebral circulation orsystemic arterial system. Those entering the cerebral circulationobstruct small arteries and lead to macroscopic or microscopic cerebralinfarction, with ensuing neurocognitive dysfunction. Systemic embolisimilarly cause infarction, leading to cardiac, renal, mesenteric, andother ischemic complications. See Barbut et al., "Aortic AtheromatosisAnd Risks of Cerebral Embolization," Journal of Cardiothoracic andVascular Anesthesia 10(1):24-30 (1996), which is incorporated herein byreference in its entirety.

Emboli entering the cerebral circulation during coronary artery bypasssurgery have been detected with transcranial Doppler ultrasonography(TCD). TCD is a standard visualization technique used for monitoringemboli in the cerebral circulation. To detect emboli using TCD, themiddle cerebral artery of a bypass patient is continuously monitoredfrom aortic cannulation to bypass discontinuation using a 2 MHZpulsed-wave TCD probe (Medasonics-CDS) placed on the patient's temple ata depth of 4.5 to 6.0 cm. The number of emboli is determined by countingthe number of embolic signals, which are high-amplitude, unidirectional,transient signals, lasting less than 0.1 second in duration andassociated with a characteristic chirping sound.

TCD is useful in analyzing the relationship between embolization andprocedures performed on blood vessels. For example, the timing ofembolic signals detected by TCD have been recorded along with the timingof procedures performed during open or closed cardiac surgicalprocedures. One of these procedures is cross-clamping of the aorta totemporarily block the flow of blood back into the heart. It has beenfound that flurries of emboli are frequently detected after aorticclamping and clamp release. During the placement and removal for theclamps, atheromatous material along the aortic wall apparently becomesdetached and finds its way to the brain and other parts of the body.Similarly, flurries of emboli are also detected during aorticcannulation and inception and termination of bypass.

Transesophageal echocardiography (TEE), another standard visualizationtechnique known in the art, is significant in the detection ofconditions which may predispose a patient to embolization. TEE is aninvasive technique, which has been used, with either biplanar andmultiplanar probes, to visualize segments of the aorta, to ascertain thepresence of atheroma. This technique permits physicians to visualize theaortic wall in great detail and to quantify atheromatous aortic plaqueaccording to thickness, degree of intraluminal protrusion and presenceor absence of mobile components, as well as visualize emboli within thevascular lumen. See, for example, Barbut et al., "Comparison ofTranscranial Doppler and Transesophageal Echocardiography to MonitorEmboli During Coronary Bypass Surgery," Stroke 27(1):87-90 (1996) andYao, Barbut et al., "Detection of Aortic Emboli By TransesophagealEchocardiography During Coronary Artery Bypass Surgery," Journal ofCardiothoracic Anesthesia 10(3):314-317 (May 1996), and Anesthesiology83(3A):A126 (1995), which are incorporated herein by reference in theirentirety. Through TEE, one may also determine which segments of a vesselwall contain the most plaque. For example, in patients with aorticatheromatous disease, mobile plaque has been found to be the leastcommon in the ascending aorta, much more common in the distal arch andmost frequent in the descending segment. Furthermore, TEE-detectedaortic plaque is unequivocally associated with stroke. Plaque of allthickness is associated with stroke but the association is strongest forplaques over 4 mm in thickness. See Amarenco et al., "Atheroscleroticdisease of the aortic arch and the risk of ischemic stroke," New EnglandJournal of Medicine 331:1474-1479 (1994).

Another visualization technique, intravascular ultrasound, is alsouseful in evaluating the condition of a patient's blood vessel. Unlikethe other techniques mentioned, intravascular ultrasound visualizes theblood vessel from its inside. Thus, for example, it may be useful forvisualizing the ascending aorta overcoming deficiencies of the othertechniques. In one aspect of the invention, it is contemplated thatintravascular ultrasound is useful in conjunction with devices disclosedherein. In this way, the device and visualizing means may be introducedinto the vessel by means of a single catheter.

Through visualization techniques such as TEE epicardial aorticultrasonography and intravascular ultrasound, it is possible to identifythe patients with plaque and to determine appropriate regions of apatient's vessel on which to perform certain procedures. For example,during cardiac surgery, in particular, coronary artery bypass surgery,positioning a probe to view the aortic arch allows monitoring of allsources of emboli in this procedure, including air introduced duringaortic cannulation, air in the bypass equipment, platelet emboli formedby turbulence in the system and atheromatous emboli from the aorticwall. Visualization techniques may be used in conjunction with a bloodfilter device to filter blood effectively. For example, through use of avisualization technique, a user may adjust the position of a bloodfilter device, and the degree of actuation of that device as well asassessing the efficacy of the device by determining whether foreignmatter has bypassed the device.

It is an object of the present invention to eliminate or reduce theproblems that have been recognized as relating to embolization. Thepresent invention is intended to capture and remove emboli in a varietyof situations, and to reduce the number of emboli by obviating the needfor cross-clamping. For example, in accordance with one aspect of theinvention, blood may be filtered in a patient during procedures whichaffect blood vessels of the patient. The present invention isparticularly suited for temporary filtration of blood in an artery of apatient to capture embolic debris. This in turn will eliminate or reduceneurologic, cognitive, and cardiac complications helping to reducelength of hospital stay. In accordance with another aspect of theinvention, blood may be filtered temporarily in a patient who has beenidentified as being at risk for embolization.

As for the devices, one object is to provide simple, safe and reliabledevices that are easy to manufacture and use. A further object is toprovide devices that may be used in any blood vessel. Yet another objectis to provide devices that will improve surgery by lesseningcomplications, decreasing the length of patients' hospital stays andlowering costs associated with the surgery. See Barbut et al.,"Intraoperative Embolization Affects Neurologic and Cardiac Outcome andLength of Hospital Stay in Patients Undergoing Coronary Bypass Surgery,"Stroke (1996).

The devices disclosed herein have the following characteristics: canwithstand high arterial blood flow rates for an extended time; include amesh that is porous enough to allow adequate blood flow in a bloodvessel while capturing mobile emboli; can be used with or withoutimaging equipment; remove the captured emboli when the operation hasended; will not dislodge mobile plaque; and can be used in men, women,and children of varying sizes.

As for methods of use, an object is to provide temporary occlusion andfiltration in any blood vessel and more particularly in any artery. Afurther object is to provide a method for temporarily filtering blood inan aorta of a patient before the blood reaches the carotid arteries andthe distal aorta. A further object is to provide a method for filteringblood in patients who have been identified as being at risk forembolization. Yet a further object is to provide a method to be carriedout in conjunction with a blood filter device and visualizationtechnique that will assist a user in determining appropriate sites offiltration. This visualization technique also may assist the user inadjusting the blood filter device to ensure effective filtration. Yet afurther object is to provide a method for filtering blood during surgeryonly when filtration is necessary. Yet another object is to provide amethod for eliminating or minimizing embolization resulting from aprocedure on a patient's blood vessel by using a visualization techniqueto determine an appropriate site to perform the procedure.

Another object is to provide a method for minimizing incidence ofthromboatheroembolisms resulting from cannula and catheter procedures bycoordinating filtration and blood flow diffusion techniques in a singledevice. Another object is to provide a method of inserting or retrievinga cannula or catheter with attached filtering means from a vessel whileminimizing the device's profile and diameter.

Thus, we disclose herein each of the individual designs listed belowwhich are grouped into three categories.

    ______________________________________                                        DESIGN         ADVANTAGE                                                      ______________________________________                                        Aortic cannula based:                                                         Mechanical Occluder                                                           1.  Basket with dam                                                                              1.    No additional holes/incisions                        2.  Basket with dam and                                                                                 required.                                                    inflatable seal                                                                               Reliable actuation mechanism.                        3.  Basket with removable                                                                              Non-migrating positioning seal.                          dam                   Stability.                                          4.  Expandable wire basket                                                                             Rugged design; will not burst                                                 (except #2)                                                                   No fluoroscopy required.                                                      Potentially less traumatic to vessel                                          than mechanical cross clamps.                        Inflatable Occluder                                                           1.  Balloon with adhesive                                                                        1.    No additional holes/incisions required                     seal                   (except #4).                                     2.  Self-inflating balloon                                                                             Conforming seal; adjusts to any                      3.  Self-inflating balloon                                                                             shape.                                                        on a collapsible. cannula                                                                     Potentially less traumatic to vessel                 4.  Balloon catheter                                                                                   than mechanical cross clamps.                        5.  Balloon catheter with                                                                              Adhesive seal reduces potential for                       aortic cannula                                                                                    leakage and adds to occluder                              introducer           stability.                                          6.  Balloon catheter with                                                                              Self-inflating units are self-sealing                         aortic cannula                                                                                occluder.                                                    introducer and guide                                                                           Catheter systems decoupled from                                               cannula. Units can be inserted to                                             desired location independent of                                               cannula position.                                                             No fluoroscopy required.                             Cardioplegia cannula based:                                                   Inflatable Occluder                                                           1.  Balloon cannula                                                                              1.    Same as other inflatable occluders                   2.  Balloon catheter                                                                                    (listed above).                                          through cannula                                                                                   Occlusion device separate from aortic                3.  Port access occiuder                                                                                       cannula. Reduces complexity of                                              critical device.                                                        Port access design does not require                                           partial or full sternotomy.                                                   No fluoroscopy required. 4.                          ______________________________________                                    

BRIEF DESCRIPTION OF DRAWINGS

Reference is next made to a brief description of the drawings, which areintended to illustrate balloon aortic cannula and catheter devices foruse herein. The drawings and detailed description which follow areintended to be merely illustrative and are not intended to limit thescope of the invention as set forth in the appended claims.

FIG. 1 is a longitudinal view of a balloon aortic cannula according toone embodiment having the filter deployed and the balloon occluder inthe contracted condition;

FIGS. 2A, 2B, and 2C are cross-sectional views through section line 2--2of the device depicted in FIG. 1, showing the balloon occluder atsuccessive degrees of inflation;

FIG. 3 is a longitudinal view of the balloon aortic cannula depicted inFIG. 1, showing the balloon occluder in the fully expanded condition anddisposed circumferentially about the blood cannula;

FIG. 4 is a longitudinal view of a balloon aortic cannula according toanother embodiment, showing the filter deployed and the balloon occluderin the contracted condition at a radial position about the distal regionof the balloon aortic cannula;

FIG. 5 is a longitudinal view of the balloon aortic cannula according toFIG. 4, showing the balloon occluder and filter deployed after insertionof the cannula into the aorta;

FIG. 6 is a longitudinal view of a balloon aortic cannula according toanother embodiment;

FIG. 7 is a longitudinal view of a balloon aortic cannula according toanother embodiment, wherein the filter mesh is continuous;

FIG. 8 is a longitudinal view of a balloon aortic cannula according toanother embodiment;

FIG. 9 is a longitudinal view of a balloon aortic cannula according toanother embodiment;

FIG. 9A is a cross-sectional view through section line A--A of thedevice depicted in FIG. 9;

FIG. 10 is a longitudinal view of a balloon aortic cannula according toanother embodiment; and

FIG. 11 is a longitudinal view of an arterial balloon catheter disposedwithin the aorta and having a balloon occluder and filter deployedtherein.

FIG. 12 is a longitudinal view of a balloon aortic cannula according toanother embodiment, wherein a flow diffuser is included at a locationdistal to the filter;

FIG. 12a is a detail of the flow diffuser of FIG. 12;

FIG. 13 is a longitudinal view of a balloon aortic cannula according toanother embodiment, wherein a flow diffuser is included at a locationdistal to the filter;

FIG. 13a is a detail of the flow diffuser of FIG. 13;

FIG. 14 is a longitudinal view of a balloon aortic cannula according toanother embodiment, wherein a flow diffuser is included at a locationproximal to the filter.

FIG. 15 is a longitudinal view of a balloon aortic cannula according toanother embodiment, wherein a flow diffuser is included at a locationproximal to the filter.

FIG. 16 is a longitudinal view of a balloon aortic cannula according toanother embodiment wherein the cannula includes a condom-like filtersleeve shown in a rolled back position.

FIG. 17 is a longitudinal view of the balloon aortic cannula of FIG. 16wherein the unrolled filter sleeve has captured the filter means.

FIG. 18 shows detail of an unrolled filter sleeve and accompanyingcontrol lines.

FIG. 19 is a three-dimensional drawing of a balloon aortic cannula witha filter sleeve in the rolled up position.

FIG. 19A shows the cannula of FIG. 19 in use.

FIG. 20 is a longitudinal view of a balloon aortic cannula including asleeve deployable by virtue of a pulley mechanism.

FIG. 21 is a longitudinal view of a balloon aortic cannula wherein thecannula has a collapsible section which can accommodate the lip of thefilter.

FIG. 22 is a longitudinal view of a balloon aortic elastic cannulawherein the cannula's outer diameter and filter profile are reduced byintroduction of a stylet in the cannula's central lumen.

FIG. 23 is a longitudinal view of a balloon aortic elastic cannulawherein the elastic cannula is in a relaxed state.

FIG. 24 is a longitudinal view of a cannula wherein the expander isproximal to the collapsible portion of the distal cannula.

FIG. 25 is a longitudinal view of a cannula wherein the expander hasbeen inserted into the collapsible portion of the distal cannula.

FIGS. 26 and 26c depict a cannula wherein the filter has an elastomericcompliant edge which conforms to vessel irregularities.

FIGS. 26a, 26b and 26d show other views of the cannula depicted in FIG.26c.

FIG. 27 shows a cannula having an open-ended sleeve disposed within theaorta.

FIG. 28 is a longitudinal view of a balloon aortic cannula wherein thefilter and balloon are of integrated construction.

FIG. 29 is a longitudinal view of a balloon aortic cannula wherein theballoon occluder contains a conduit for delivery of solutions to theheart side of the occluder.

FIG. 30 is a longitudinal view of a catheter as in FIG. 11 wherein thecatheter contains openings and lumens for delivery of solutions to theheart side of the balloon occluder.

FIG. 31 is a longitudinal view of a cannula with blocking dam.

FIGS. 32 and 32A are longitudinal views of a balloon occluder oncatheter.

FIGS. 33 and 33A are longitudinal views of a cannula with self-expandingballoon.

FIG. 34 is a longitudinal view of an adhesive coated balloon cannula.

FIGS. 35 and 35A are longitudinal views of an expandable wire occluder.

FIG. 36 is a longitudinal view of a cannula introducer.

FIG. 37 is a longitudinal view of an integrated occlusion cape.

FIG. 38 is a longitudinal view of a cardioplegia occlusion cannula inuse.

FIG. 39 is a longitudinal view of a cannula with occluder guide.

FIG. 40 is a depiction of the sternum and aorta of a patient having anocclusion cannula in use.

FIG. 41 is a longitudinal view of an L-shaped single-piece occluder.

FIG. 42 is a longitudinal view of a J-shaped single-piece occluder.

FIG. 43 is a depiction of a multiple component port access aorticoccluder.

FIG. 44 is a longitudinal view of a balloon aortic cannula in use.

FIG. 45 is a longitudinal view of a cardioplegia cannula and ballooncatheter in use.

FIG. 46 is a longitudinal view of a cardioplegia balloon cannula in use.

DETAILED DESCRIPTION

To filter blood effectively, i.e., to capture embolic material, withoutunduly disrupting blood flow, the mesh must have the appropriatephysical characteristics, including area (A_(M)), thread diameter(D_(T)), and pore size (S_(P)). In the aorta, the mesh 40 must permitflow rates as high as 3 L/min or more, more preferably 3.5 L/min ormore, more preferably 4 L/min or more, more preferably 4.5 L/min ormore, more preferably 5 L/min or more preferably 5.5 L/min or more, andmost preferably 6 L/min or more at pre-filter pressures (proximal to themesh) of around 120 mm Hg or less.

In order to capture as many particles as possible, mesh with theappropriate pore size must be chosen. The dimensions of the particles tobe captured is an important factor in this choice. In the aorta duringcardiac surgery, for example, individual particle diameter has beenfound to range from 0.27 mm to 2.88 mm, with a mean diameter of 0.85 mm,and individual particle volume has been found to range from 0.01 mm³ to12.45 mm³, with a mean particle volume of 0.32 mm³. Approximately 27percent of the particles have been found to measure 0.6 mm or less indiameter. During cardiac bypass surgery in particular, the total aorticembolic load has been found to range from 0.57 cc to 11.2 cc, with amean of 3.7 cc, and an estimated cerebral embolic load has been found torange from 60 mm³ to 510 mm³, with a mean of 276 mm³.

By way of example, when a device as disclosed herein is intended for usein the aorta, the area of the mesh required for the device is calculatedin the following manner. First, the number of pores N_(P) in the mesh iscalculated as a function of thread diameter, pore size, flow rate,upstream pressure and downstream pressure. This is done usingBernoulli's equation for flow in a tube with an obstruction: ##EQU1##

In this equation, P is pressure, ρ is density of the fluid, g is thegravity constant (9.8 m/s²), V is velocity, K represents the lossconstants, and f is the friction factor. The numbers 1 and 2 denoteconditions upstream and downstream, respectively, of the filter.

The following values are chosen to simulate conditions within the aorta:

P₁ =120 mm Hg;

P₂ =80 mm Hg;

K_(entry) =0.5;

K_(exit) =1.0;

K=K_(entry) +K_(exit) ; and ##EQU2## Assuming laminar flow out of themesh filter, f is given as ##EQU3## where Re is the Reynold's number andthe Reynold's number is given by the following equation: ##EQU4## whereμ is the kinematic viscosity of the fluid and A_(h) is the area of onehole in the mesh given by S_(P) *S_(P).

Conservation of the volume dictates the following equation: ##EQU5##where Q is the flow rate of the blood. In addition, V₁ is given by:##EQU6## where A_(vessel) is the cross-sectional area of the vessel.Substitution and manipulation of the above equations yields N_(P).

Next, the area of the mesh is calculated as a function of the number ofpores, thread diameter and pore size using the following equation:

    A.sub.M =N.sub.P *(D.sub.T +S.sub.P).sup.2

In an embodiment of the device 10 that is to be used in the aorta, meshwith dimensions within the following ranges is desirable: mesh area is3-10 in², more preferably 4-9 in², more preferably 5-8 in² morepreferably 6-8 in², most preferably 7-8 in² ; mesh thickness is 20-280μm, more preferably 23-240 μm, more preferably 26-200 μm, morepreferably 29-160 μm, more preferably 32-120 μm, more preferably 36-90μm, more preferably 40-60 μm; thread diameter is 10-145 μm, morepreferably 12-125 μm, more preferably 14-105 μm, more preferably 16-85μm, more preferably 20-40 μm; and pore size is 50-300 μm, morepreferably 57-285 μm, more preferably 64-270 μm, more preferably 71-255μm, more preferably 78-240 μm, more preferably 85-225 μm, morepreferably 92-210 μm, more preferably 99-195 μm, more preferably 106-180μm, more preferably 103-165 μm, more preferably 120-150 μm. In apreferred embodiment of the invention, mesh area is 3-8 in², meshthickness is 36-90 μm, thread diameter is 16-85 μm, and pore size is103-165 μm. In a further preferred embodiment of the invention, mesharea is 3-5 in², mesh thickness is 40-60 μm, thread diameter is 20-40μm, and pore size is 120-150 μm.

The calculation set forth above has been made with reference to theaorta. It will be understood, however, that blood flow parameters withinany vessel other than the aorta may be inserted into the equations setforth above to calculate the mesh area required for a blood filterdevice adapted for that vessel.

To test the mesh under conditions simulating the conditions within thebody, fluid flow may be observed from a reservoir through a pipeattached to the bottom of the reservoir with the mesh placed over themouth of the pipe through which the fluid exits the pipe. A mixture ofglycerin and water may be used to simulate blood. Fluid height (h) isthe length of the pipe in addition to the depth of the fluid in thereservoir, and it is given by the following equation: ##EQU7## where ρis given by the density of the glycerin-water mixture, and g is given bythe gravity constant (9.8 ms²).

Bernoulli's equation (as set forth above) may be solved in order todetermine (D_(T) /S_(P))_(Equiv). V₁ is given by the following equation:##EQU8## where Q is the flow rate which would be measured during testingand A₁ is the cross-sectional area of the pipe. V₂ is given by thefollowing equation: ##EQU9## where N is the number of pores in the meshand A₂ is the area of one pore. Further, P₁ =120 mm Hg and P₂ =0 mm Hgand S_(P) is the diagonal length of the pore. Reynold's number (Re) isgiven by the following equation: ##EQU10## where ρ and μ are,respectively, the density and kinematic viscosity of the glycerin-watermixture.

Once appropriate physical characteristics are determined, suitable meshcan be found among standard meshes known in the art. For example,polyurethane meshes may be used, such as Saati and Tetko meshes. Theseare available in sheet form and can be easily cut and formed into adesired shape. In a preferred embodiment, the mesh is sonic welded intoa cone shape. Other meshes known in the art, which have the desiredphysical characteristics, are also suitable. Anticoagulants, such asheparin and heparinoids, may be applied to the mesh to reduce thechances of blood clotting on the mesh. Anticoagulants other thanheparinoids also may be used, e.g., monoclonal antibodies such as ReoPro(Centocore). The anticoagulant may be painted or sprayed onto the mesh.A chemical dip comprising the anticoagulant also may be used. Othermethods known in the art for applying chemicals to mesh may be used.

In an embodiment of the devices suited for placement in the aorta, theexpansion means, upon deployment, has an outer diameter of approximately100 Fr., more preferably 105 Fr., more preferably 110 Fr., morepreferably 115 Fr., more preferably 120 Fr., and most preferably 125Fr., or greater, and an inner diameter of approximately 45 Fr. (1Fr.=0.13 in.) when fully inflated. The dimensions of the expansion meansmay be adjusted in alternative embodiments adapted for use in vesselsother than the aorta. Alternatively, expandable members other than aballoon also may be used with this invention. Other expandable membersinclude the umbrella frame with a plurality of arms as described in U.S.application Ser. Nos. 08/533,137, 08/580,223, 08/584,759, 08/640,015,08/842,727, and 08/852,867.

All components of this device should be composed of materials suitablefor insertion into the body. Additionally, sizes of all components aredetermined by dimensional parameters of the vessels in which the devicesare intended to be used. These parameters are known by those skilled inthe art.

By way of purely illustrative example, the operational characteristicsof a filter according to the invention and adapted for use in the aortaare as follows:

    ______________________________________                                        Temperature Range                                                                           25-39 degrees C.                                                Pressure Range                                                                                       50-150 mm Hg                                           Flow Rate                   usually up to 5 L/min., can be as high as 6                                                    L/min.                           Duration of single use                                                                       up to approximately 5 hours                                    Average emboli trapped                                                                       5-10,000                                                       Pressure gradient range                                                                     (100-140)/(50-90)                                               ______________________________________                                    

Modification of the operational characteristics set forth above for usein vessels other than the aorta are readily ascertainable by thoseskilled in the art in view of the present disclosure. An advantage ofall embodiments disclosed herein is that the blood filter will captureemboli which may result from the incision through which the blood filteris inserted. Another advantage is that both the balloon occluder and thefilter means enter the vessel through the same incision created for theblood cannula, and therefore the devices and methods herein economize onincisions made in the blood vessel, often the aorta.

In addition, use of visualization techniques is also contemplated inorder to determine which patients require filtration (identify riskfactors), where to effectively position a blood filter device tomaximize effectiveness, when to adjust the device if adjustment isnecessary, when to actuate the device and appropriate regions forperforming any procedures required on a patient's blood vessel.

In accordance with one aspect of the invention, a visualizationtechnique, such as TCD, is used to determine when to actuate a bloodfilter device. For example, during cardiac bypass surgery, flurries ofemboli are detected during aortic cannulation, inception, andtermination of bypass and cross-clamping of the aorta. Therefore, a meshmay be opened within a vessel downstream of the aorta during theseprocedures and closed when embolization resulting from these procedureshas ceased. Closing the mesh when filtration is not required helps tominimize obstruction of the blood flow.

According to another embodiment, a visualization technique is used tomonitor emboli entering cerebral circulation to evaluate theeffectiveness of a blood filter device in trapping emboli. Also, avisualization technique is useful to positioning a device within avessel so that it operates at optimum efficiency. For example, a usermay adjust the position of the device if TCD monitoring indicates emboliare freely entering the cerebral circulation. In addition, a user mayadjust a mesh of a blood filter device to ensure that substantially allof the blood flowing in the vessel passes through the mesh.

According to yet another embodiment, a visualization technique, such asintravascular ultrasonography, TEE, and epicardial aorticultrasonography, is used to identify those patients requiring bloodfiltration according to the present invention. For example, thesevisualization techniques may be used to identify patients who are likelyto experience embolization due to the presence of mobile plaque. Thesetechniques may be used before the patient undergoes any type ofprocedure which will affect a blood vessel in which mobile plaque islocated.

Additionally, visualization techniques may be used to select appropriatesites on a blood vessel to perform certain procedures to eliminate orreduce the occurrence of embolization. For example, during cardiacbypass surgery, the aorta is both clamped and cannulated. According tomethods disclosed herein, the step of clamping may be replaced bydeployment of a balloon occluder. These procedures frequently dislodgeatheromatous material already present on the walls of the aorta. Tominimize the amount of atheromatous material dislodged, a user may clampor cannulate a section of the aorta which contains the least amount ofatheromatous material, as identified by TEE, epicardial aorticultrasonography or other visualization technique such as intravascularultrasonography.

Procedures other than incising and clamping also tend to dislodgeatheromatous material from the walls of vessels. These proceduresinclude, but are not limited to, dilatation, angioplasty, andatherectomy.

Visualization techniques also may be used to select appropriate sitesfor filtering blood. Once atheromatous material is located within avessel, a blood filter device may be placed downstream of that location.

Visualization techniques, other than those already mentioned, as areknown to those skilled in the art, are also useful in ascertaining thecontours of a blood vessel affected by surgical procedure to assess avariety of risk of embolization factors, and to locate appropriatesections of a vessel for performing certain procedures. Any suitablevisualization device may be used to evaluate the efficacy of a device,such as those disclosed herein, in trapping emboli.

In one embodiment, a balloon aortic cannula with associated filter isprovided as depicted in FIG. 1. The balloon aortic cannula may include apressurizing cannula 50 having a proximal region, a distal region, andan intermediate region which connects the proximal and distal regions.The pressurizing cannula 50 is typically a rigid or semi-rigid,preferably transparent tube having a first substantially cylindricallumen which extends from the proximal region to the distal region and isshaped to receive blood supply cannula 10 or an additional side port(not shown). The pressurizing cannula 50 may further include a secondlumen 60 in fluid communication with balloon occluder 65 disposed aboutthe distal region of pressurizing cannula 50. With reference to FIG. 1,balloon occluder 65 is shown in the deflated, contracted condition,having a minimal cross-sectional diameter for entry through an incisionin aorta 99. Lumen 60 is adapted to inflate balloon occluder 65 by useof a gas, or preferably saline, under pressure. The proximal end of thecannula 50 may include any of the features disclosed in U.S. applicationSer. Nos. 08/553,137, 08/580,223, and 08/584,759.

Blood supply cannula 10 may have certain features in common with astandard arterial cannula and is generally a substantially cylindrical,semi-rigid, and preferably transparent tube. The blood cannula isslidable within the pressurizing cannula, and the blood cannula willtypically include a fitting or molded joint at its proximal end (notshown) which is adapted for coupling to a bypass-oxygenator system, andmay have any of the features disclosed in U.S. application Ser. Nos.08/553,137, 08/580,223, and 08/584,759. Blood cannula 10 is adapted tocarry blood to the aorta from the bypass-oxygenator system.

With reference to FIG. 1, the distal region of pressurizing cannula 50is shown with blood filtration means deployed in the ascending region ofa human aorta 99. The distal region of pressurizing cannula 50 includesa plurality of spokes or holding strings 55 made from Dacron® or othersuitable material. Holding strings 55 connect the distal region of thepressurizing cannula 50 to an expansion means 70, preferably aninflation seal which comprises a continuous ring of thin tubing attachedto filter mesh 75 on its outer side. Filter mesh 75 is bonded at itsdistal end around the circumference of blood cannula 10, preferably at across-sectional position near the distal end of blood cannula 10.

Inflation seal 70 may be constructed from elastomeric or non-elastomerictubular material which encloses a donut-shaped chamber. When deployed,the inflation seal will expand to a diameter which fits tightly againstthe lumen of aorta 99. The inflation seal will thus be capable ofexpansion to an outer diameter of at least 1 cm, more preferably atleast 1.5 cm, more preferably at least 2 cm, more preferably at least2.5 cm, more preferably at least 3 cm, more preferably at least 3.5 cm,more preferably at least 4 cm, more preferably at least 4.5 cm, morepreferably at least 5 cm, more preferably at least 5.5 cm, morepreferably at least 6 cm. These ranges cover suitable diameters for bothpediatric use and adult use. The inflation seal is typically acontinuous ring of very thin tubing attached on one side to the filtermesh and on the other side to the pressurizing cannula by holdingstrings.

The inflation seal should be able to maintain an internal pressure inchamber 319, without bursting, of greater than 55 mm Hg, more preferablygreater than 60 mm Hg, more preferably greater than 70 mm Hg, morepreferably greater than 80 mm Hg, more preferably greater than 90 mm Hg,more preferably greater than 100 mm Hg, more preferably greater than 110mm Hg, more preferably greater than 120 mm Hg, more preferably greaterthan 130 mm Hg, more preferably greater than 140 mm Hg, more preferablygreater than 150 mm Hg. The internal pressure needed will depend on thepressure maintained in the aorta against the mesh. Thus, if the aorticpressure is 55 mm Hg, then the pressure in the inflation seal must begreater than 55 mm Hg to prevent leakage around the seal. Typically, theaortic pressure will be at least 75 mm Hg because this level of pressureis needed to ensure adequate brain perfusion. It will be recognized thatsuch inflation seal pressures are much higher than the maximum levelthat can be used in the pulmonary venous system because the veins andarteries therein will typically hold no more than about 40-50 mm Hg, orat most 60 mm Hg without rupture.

Chamber 71 is in fluid communication with a first tubular passage 56 anda second tubular passage 57 which permit chamber 71 to be inflated withgas, or preferably a fluid such as saline. Passage 57 is in fluidcommunication with a third lumen of pressurizing cannula 50 (not shown),while passage 56 is in fluid communication with a fourth lumen ofpressurizing cannula 50 (not shown). Passages 56 and 57 therebyinterconnect chamber 71 with the third and fourth lumens, respectively,of pressurizing cannula 50.

In certain embodiments, inflation seal 70 will include a septum (notshown) which blocks the movement of fluid in one direction aroundchamber 71. If the septum is positioned in close proximity to the fluidentry port, then the injection of fluid will push all gas in chamber 71around inflation seal 70 and out through passage 56. In one embodiment,the entry port and the exit port are positioned in close proximity, withthe septum disposed between the entry and exit port. In this case,injection of fluid will force virtually all gas out of inflation seal70.

Filter mesh 75 is bonded at its proximal end to inflation seal 70 and atits distal end to blood cannula 10. Mesh 75 can be made of a materialwhich is reinforced or non-reinforced. Mesh 75, when expanded as shownin FIG. 1, may assume a substantially conical shape with a truncateddistal region. The mesh should be formed of a material having a poresize which obstructs objects 5 mm in diameter or less, more preferably 3mm in diameter, more preferably less than 3 mm, more preferably lessthan 2.75 mm, more preferably less than 2.5 mm, more preferably lessthan 2.25 mm, more preferably less than 2 mm, more preferably less than1.5 mm, more preferably less than 1 mm, more preferably less than 0.75mm, more preferably less than 0.5 mm, more preferably less than 0.25 mm,more preferably less than 0.1 mm, more preferably less than 0.075 mm,more preferably less than 0.05 mm, more preferably less than 0.025 mm,more preferably 0.02 mm, and down to sizes just larger than a red bloodcell. It will be understood that for a given pore size that blocksparticles of a certain size as stated above, that pore size will blockall particles larger than that size as well. It should also beunderstood that the necessary pore size is a function of bloodthroughput, surface area of the mesh, and the pressure on the proximaland distal side of the mesh. For example, if a throughput of 5-6 L/min.is desired at a cross-section of the aorta having a diameter of 40 mm,and a pressure of 120 mm Hg will be applied to the proximal side of themesh to obtain a distal pressure of 80 mm Hg, then a pore size of about≧50 μm is needed. By contrast, in the pulmonary artery the samethroughput is needed, but the artery cross-section has a diameter ofonly 30 mm. Moreover, the proximal pressure is typically 40-60 mm Hg,while the distal pressure is about 20 mm Hg. Thus, a much larger poresize is needed to maintain blood flow. If pore sizes as disclosed hereinfor the aorta were used in the pulmonary artery, the blood throughputwould be insufficient to maintain blood oxygenation, and the patientwould suffer right ventricular failure because of pulmonary arteryhypertension.

Much like the inflation seal, the balloon occluder 65 may be constructedfrom elastomeric or non-elastomeric material and, with reference to FIG.3, comprises a continuous ring of tubing which encloses a tubularchamber 66 disposed circumferentially about the pressurizing cannula 50and blood cannula 10. FIGS. 2A, 2B, and 2C illustrate deployment ofballoon occluder 65 within aorta 99. When pressurized saline passesthrough lumen 60, balloon occluder 65 expands to a diameter which fitstightly against the inner wall of aorta 99. The balloon occluder willthus be capable of expansion to an outer diameter of at least 1 cm, morepreferably at least 1.5 cm, more preferably at least 2 cm, morepreferably at least 2.5 cm, more preferably at least 3 cm, morepreferably at least 3.5 cm, more preferably at least 4 cm, morepreferably at least 4.5 cm, more preferably at least 5 cm, morepreferably at least 5.5 cm, more preferably at least 6 cm. FIG. 3depicts a longitudinal view of the balloon aortic cannula with balloonoccluder 65 fully expanded within aorta 99 and thereby occludingretrograde flow of blood in the ascending aorta.

With reference to FIG. 3, balloon occluder 65 should be able to maintainan internal pressure in chamber 66, without bursting, of greater than 55mm Hg, more preferably greater than 60 mm Hg, more preferably greaterthan 70 mm Hg, more preferably greater than 80 mm Hg, more preferablygreater than 90 mm Hg, more preferably greater than 100 mm Hg, morepreferably greater than 110 mm Hg, more preferably greater than 120 mmHg, more preferably greater than 130 mm Hg, more preferably greater than140 mm Hg, more preferably greater than 150 mm Hg. The internal pressureneeded will depend on the pressure maintained in the aorta against theballoon occluder. Thus, if the aortic pressure is 55 mm Hg, then thepressure in the balloon occluder must be greater than 55 mm Hg toprevent leakage around the balloon occluder. Typically, the aorticpressure will be at least 75 mm Hg because this level of pressure isneeded to ensure adequate brain perfusion. It will be recognized thatsuch balloon occluder pressures are much higher than the maximum levelthat can be used in the pulmonary venous system because the veins andarteries therein will typically hold no more than about 40-50 mm Hg, orat most 60 mm Hg without rupture.

In certain embodiments, the pressurizing cannula 50 will be providedwith an additional lumen (not shown) in fluid communication with balloonoccluder 65. A system having two lumens in communication with balloonoccluder 65 can be used to enter saline into the balloon occluder andpurge all gas therefrom to prevent the formation of an air embolism in apatient's circulation should the balloon occluder rupture during use.Thus, if pressurized saline is advanced through lumen 60, the gaspresent in balloon occluder 65 will be forced out through the additionallumen in communication with the balloon occluder. A septum may beincluded in the balloon occluder and disposed between entry and exitports to ensure that all gas is purged on entry of saline.

It will also be understood for this cannula apparatus that blood flow tothe patient is maintained by blood passage through blood cannula 10, andnot through mesh 75. Thus, the cannula must have an inner diameter whichallows blood throughput at a mean flow rate of at least 3.0 L/min., morepreferably 3.5 L/min., more preferably 4 L/min., more preferably atleast 4.5 L/min., more preferably at least 5 L/min., and more. Ofcourse, flow rate can vary intermittently down to as low as 0.5 L/min.Therefore, the inner diameter of blood supply cannula 10 will typicallybe at least 9 F (3.0 mm), more preferably 10 F, more preferably 11 F,more preferably 12 F (4 mm), more preferably 13 F, more preferably 14 F,more preferably 15 F (5 mm), and greater. Depending on the innerdiameter and thickness of the tubing, the outer diameter of bloodcannula 10 is approximately 8 mm. Meanwhile, the pressurizing cannula 50may have an outer diameter of approximately 10.5 mm. The foregoingranges are intended only to illustrate typical device parameters anddimensions, and the actual parameters may obviously vary outside thestated ranges and numbers without departing from the basic principlesdisclosed herein.

In use, the balloon aortic cannula with associated filter is provided,and saline is injected into both the balloon occluder and the inflationseal until saline exits from the exit ports and exit lumens, therebypurging substantially all gas from the inflation seal, the balloonoccluder, and dual lumen systems associated with each. Cardiac surgerycan then be conducted in accordance with procedures which employstandard cannula insertion, as discussed more fully herein. The mesh 75,inflation seal 70, and balloon occluder 65 are maintained in a deflated,fully contracted condition about the pressurizing cannula and/or bloodcannula. The cannula is introduced into the aorta, preferably theascending aorta, of a patient through an incision, and the incision maybe tightened about the cannula by use of a "purse string" suture.Cardiopulmonary bypass occurs through blood cannula 10.

With the cannula in place, the filter is ready for deployment. Thefiltration means are first exposed by removing a handle or enclosurewhich may cover the expansion means and mesh. Then, saline or gas isadvanced under pressure through lumen 57 to expand the inflation seal.The inflation seal expands to ensure contact with the inside of theaorta at all points along the circumference of the lumen, as depicted inFIGS. 1 and 2C. The inflation system for the expansion means is thenlocked in place to prevent inflation or depressurization of theinflation seal during use.

The balloon occluder 65 is then deployed to occlude the aorta upstreamof the filter. Saline or gas is advanced under pressure through lumen 60to expand the balloon occluder, as shown in FIGS. 2A, 2B, 2C, and 3.Embolic material dislodged from the aorta is captured by filter mesh 75.The bypass-oxygenator system is then started to achieve cardiopulmonarybypass through blood cannula 10. Cardiac surgery is performed while thefilter, inflation seal, and balloon occluder are maintained in place fora number of hours, typically 8 hours or less, more typically 7 hours orless, more typically 6 hours or less, more typically 5 hours or less,more typically 4 hours or less, more typically 3 hours or less, moretypically 2 hours or less, and, more typically 1 hour or less.

At the end of the cardiac surgery, the balloon occluder isdepressurized, and any embolic material dislodged by this step iscaptured by the filter. The filter is then depressurized and removedfrom the ascending aorta. The syringe lock is released and saline iswithdrawn from the balloon occluder, and then from the inflation seal.This will cause both the balloon occluder and inflation seal to contractto a deflated condition with minimum cross-sectional diameter, as thedevice was configured before deployment. Notably, embolic materialcollected in the filter is trapped under the contracted filter. Once theinflation seal, associated filter, and balloon occluder have beendeflated, the cannula can be removed from the patient without damagingthe aortic incision by using standard procedures.

The devices disclosed herein may optionally include a handle adapted tocover and enclose the inflation seal, mesh, and balloon occluder.Moreover, before deployment, the inflation system for either the balloonoccluder, inflation seal, or both, may be carried by either thepressurizing cannula or the blood cannula. In certain embodiments, theblood cannula and pressurizing cannula will be integrally combined intoa single unitary component, or the pressurizing cannula is eliminatedand the inflation system may be carried either within or on the outsideof the blood cannula.

In another embodiment, a balloon aortic cannula is provided as depictedin FIG. 4, with balloon occluder 65 disposed at one radial position on aside of pressurizing cannula 50. It will be understood that FIG. 4shares many features in common with FIGS. 1 and 3, and the numbering ofapparatus components has been duplicated so that appropriate descriptioncan be found with reference to FIGS. 1 and 3. With reference to FIG. 4,balloon occluder 65 is shown in the deflated, contracted state on a sideof pressurizing cannula 50 and disposed about the distal region thereof.Rotational orientation marker 51 may be included in certain embodimentsand disposed at a fixed radial position relative to the point ofattachment of balloon occluder 65, e.g., at a radial position 180° fromballoon occluder 65. The inclusion of a marker on the proximal region ofthe pressurizing cannula 50 will enable rotation of the cannula onceinserted in the aorta in order to ensure positioning of balloon occluder65 so that expansion and balloon occlusion occurs upstream of filter 75,and does not interfere with blood cannula 10 and/or pressurizing cannula50. Alternatively, where the pressurizing cannula 50 or blood cannula 10includes a lumen 60 which is visible on the exterior sheath, the lumen60 may be used as a rotational orientation marker.

Upon inflation, balloon occluder 65 assumes a shape as depicted in FIGS.5 or 6. With reference to FIG. 5, the occlusion chamber 65 is shownconnected to the cannula by way of a tubular extension 67 whichdistances the balloon occluder from the cannula. Alternatively, as shownin FIG. 6, the chamber of balloon occluder 65 may be in close contactwith pressurizing cannula 50 or blood cannula 10.

It will be understood that the balloon occluders as disclosed herein anddepicted on balloon aortic cannulas may be used in combination with anyof a number of arterial cannulas having associated filtration means aspreviously disclosed. Thus, the balloon occluders disclosed herein canbe used in combination with any of the arterial cannulas disclosed inBarbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996,Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28,1995, Barbut et al., U.S. application Ser. No. 08/553,137, filed Nov. 7,1995, Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr.30, 1996, Barbut et al., U.S. application Ser. No. 08/842,727, filedApr. 16, 1997, and Maahs et al., U.S. application Ser. No. 08/853,165,filed May 8, 1997, and any of the features disclosed in theseapplications can be used on the balloon aortic cannulas describedherein. Accordingly, the entire disclosures of these prior applicationsare incorporated herein by reference, and it is noted that the devices,methods, and procedures disclosed in these applications can be used incombination with the balloon occluder and balloon aortic cannuladisclosed herein.

In another embodiment, a cannula is provided as depicted in FIG. 7 witha continuous filter mesh which extends beyond and over the lumen of theblood cannula so that blood from the cannula passes through the meshbefore circulating within the patient. The device may include apressurizing cannula 50, a blood cannula, inflation seal 70, continuousmesh 75, and balloon occluder 65 which operates upstream of mesh 75. Instill another embodiment, the continuous filter mesh is tethered fromthe distal end of cannula 50 by a plurality of holding strings 55, asdepicted in FIG. 8. It will be understood that FIGS. 7 and 8 share manyfeatures in common with FIGS. 4 and 6, and the numbering of apparatuscomponents has been duplicated so that appropriate description can befound with reference to FIGS. 4 and 6.

In anther embodiment, a balloon aortic cannula is provided as depictedin FIG. 9. The device includes a pressurizing cannula 300 havingproximal region 301, distal region 302, and an intermediate region whichconnects the proximal and distal regions. The pressurizing cannula 300is typically a rigid or semi-rigid, preferably transparent tube having afirst substantially cylindrical lumen 303 which extends from theproximal region and is shaped to receive blood supply cannula 350. Thepressurizing cannula 300 further includes at its proximal region luerfittings 304 and 305 which are shaped to receive a cap or septum 306 anda syringe 307 filled with saline or gas and having a locking mechanism308 for locking the barrel 309 and plunger 310 in a fixed position. Thepressurizing cannula 300 typically has a dual lumen to affectpressurization of the inflation seal. Thus, luer 305 is connected topassage 311 which is in fluid communication with a second lumen 312which extends from the proximal to the distal end of pressurizingcannula 300. Meanwhile, luer 304 is connected to passage 313 which is influid communication with a third lumen 314 which extends from theproximal to the distal end of pressurizing cannula 300. At its distalregion, the pressurizing cannula 300 includes a blood filtrationassembly 315.

Blood supply cannula 350 may have certain features in common with astandard cannula, and is generally a substantially cylindrical,semi-rigid, and preferably transparent tube which includes a rib 351disposed about the circumference at a distal region thereof. The bloodcannula is slidable within the pressurizing cannula, and in the proximalregion, the blood cannula 350 may be angled to adopt a shape which doesnot interfere with syringe 307. Moreover, the blood cannula willtypically include a fitting or molded joint 352 which is adapted forcoupling to a bypass-oxygenator system. Blood cannula 350 is adapted tocarry blood to the aorta from the bypass-oxygenator system.

The pressurizing cannula may also include an inserting and retractinghandle 380 comprising a substantially cylindrical tube disposed aboutthe intermediate region of pressurizing cannula 300. Handle 380 willgenerally include a rigid or semi-rigid, preferably transparent tubewith molded hand grip to facilitate holding and inserting. Withreference to FIG. 9, handle 380 is slidable relative to the pressurizingcannula 300, and may include a sealing member 381 comprising a rubberwasher or O-ring mounted in a proximal region of the handle and disposedbetween 380 and pressurizing cannula 300 to prevent leakage of bloodtherebetween. Handle 380 may include corrugation ribs 382 in itsproximal and intermediate regions, and a substantially flat or levelcollar insertion region 383 adapted to fit tightly against vesselmaterial at an aortic incision. In certain embodiments, collar insertionregion 383 will include a sealing ring or rib (not shown), having awidth of about 5 mm and an outer diameter of about 13 mm, which servesas an anchor against the aorta to prevent the cannula assembly fromslipping out during a surgical procedure. A "purse string" suture isgenerally tied around the circumference of the aortic incision, and thisstring will be tightened around the ring in collar region 383 to preventslippage of the cannula assembly.

Handle 380 may also include an enlarged end region 384 which enclosesthe blood filtration assembly 315 as described in Barbut et al., U.S.application Ser. No. 08/640,015, filed Apr. 30, 1996. This housingenclosure 384 is a particularly preferred component because it preventsinadvertent deployment of the blood filtration assembly and balloonoccluder, and it provides a smooth outer surface to the cannula whichfacilitates entry through an incision in the aorta without tearing theaorta. In the absence of such housing enclosure, the balloon and filterare liable to scrape against the inner wall of a vessel, and therebydamage or rupture the vessel. At its distal end, handle 380 may includeinverted cuff 385 which bears against rib 351 of blood cannula 350 toform a seal when the filtration assembly 315 is enclosed by handle 380.

The distal region of pressurizing cannula 300 is shown with bloodfiltration assembly 315 deployed in the ascending aorta 399 of a human.Handle 380 has been moved proximally to expose filter assembly 315. Thedistal region of pressurizing cannula 300 includes a plurality ofholding strings 316 made from Dacron® or other suitable material.Holding strings 316 connect the distal region of the pressurizingcannula 300 to inflation seal 317 as described above. The inflation sealis attached to filter mesh 318 on its outer side. Filter mesh 318 isbonded at its distal end around the circumference of blood cannula 350preferably at a cross-sectional position which closely abuts rib 351.

Chamber 319 is in fluid communication with a first tubular passage 320and a second tubular passage 322 which permit chamber 319 to be inflatedwith gas, or preferably a fluid such as saline. Passage 320 is in fluidcommunication with second lumen 312 of pressurizing cannula 300, whilepassage 322 is in fluid communication with third lumen 314 ofpressurizing cannula 300. Passages 320 and 322 thereby interconnectchamber 319 with the second and third lumen 312 and 314, respectively,of pressurizing cannula 300.

In certain embodiments, inflation seal 317 will include a septum 321which blocks the movement of fluid in one direction around chamber 319.If septum 321 is positioned in close proximity to the fluid entry port,then the injection of fluid will push all gas in chamber 319 aroundinflation seal 317 and out through passage 322, as described above. Inone embodiment, the entry port and the exit port are positioned in closeproximity with septum 321 disposed between the entry and exit port. Inthis case, injection of fluid will force virtually all gas out ofinflation seal 317.

With reference to FIG. 9, the pressurizing cannula 300 may furtherinclude balloon occluder 65 operably attached at a distal region ofpressurizing cannula 300, and generally proximal to the filtrationassembly 315. Balloon occluder 65 will, upon inflation, expand upstreamof the aortic incision and filtration assembly 315 to occlude a regionof the ascending aorta as described above. In those embodiments whichinclude handle 380, balloon occluder 65 will pass through an opening inhandle 380 in order to define a chamber which is in fluid communicationwith an additional, fourth lumen (not shown) of pressurizing cannula300. A cross-sectional view of pressurizing cannula 300 and handle 380in the region of balloon occlude 65 is depicted in FIG. 9A. Withreference to FIG. 9A, balloon occluder 65 passes through opening 386 inhandle 380.

In yet another embodiment, a balloon aortic cannula is provided asdepicted in FIG. 10. The device includes blood filtration system 410which comprises insertion tube 420, umbrella frame 430, end plate 460,activation tube 450, mesh 440, adjustment device 470, and handle 480.Filtration assembly 410 is introduced into a vessel through main port407 of cannula 405, and blood or other surgical equipment may beintroduced into main port 407 of cannula 405 through side port 403. Thecannula 405 and filtration system 410 will not interfere with placementof equipment which may be used during a surgical procedure.

Umbrella frame 430 comprises a plurality of arms 432 (some of which arenot shown), which may include 3 arms, more preferably 4 arms, morepreferably 5 arms, more preferably 6 arms, more preferably 7 arms, morepreferably 8 arms, more preferably 9 arms, and most preferably 10 arms.Socket 434 may be connected to insertion tube 420 by welding, epoxy,sonic welding, or adhesive bonding. A further detailed description ofthe construction of filtration assembly 410 can be found with referenceto Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9,1996, and other references cited herein.

End plate 460 comprises a one-piece injection molded component, made ofplastic or metal. Arms 432 are bonded to end plate 460 at arm junctures461 spaced at equal increments along a circumference of a circle.Activation tube 450 extends from end plate 460 through insertion tube420 to adjustment device 470 housed in handle 480 as shown in FIG. 10.Adjustment device 470 is a linear actuation device, comprising thumbswitch 472 which is attached to guide frame 474 which is in turnattached to activation tube 450 via a bond joint. Thumb switch 472comprises base 476 and rachet arm 478 which moves along rachet slot 482along the top of handle 480, locking in predetermined intervals in amanner known in the art. Sliding thumb switch 472 away from distal end402 of cannula 405 retracts activation tube 450, which in turn draws endplate 460 toward handle 480. This movement causes arms 432 of umbrellaframe 430 to bend and causes mesh 440 to open and ready to captureembolic material in the blood. Sliding thumb switch 472 toward distalend 402 of cannula 405 pushes activation tube 450 in the direction ofmesh 440. Activation tube 450 then pushes end plate 460 away from handle480, causing arms 432 of umbrella frame 430 to straighten and mesh 440to close.

With reference to FIG. 10, filtration device 410 further includesballoon occluder 465 connected to a further lumen (not shown) on cannula405. Accordingly, the assembly provides balloon occluder 465 at a distalregion of cannula 405 so that, upon deployment, balloon occluder 465expands upstream of the filtration assembly, which assembly capturesembolic material dislodged upon deployment of balloon 465.

In another embodiment, an arterial balloon catheter is provided asdepicted in FIG. 11. The catheter includes flexible elongate member 100having an outer surface, a distal region 101, and a proximal region. Thecatheter includes balloon occluder 65 at the distal end of the elongatemember. The catheter also includes at its distal region expansion means,such as inflation seal 70, filter mesh 75 attached to inflation seal 70,and may optionally include holding strings 55 which secure the inflationseal to catheter 100. The catheter may also include an inflation system(not shown) to operate inflation seal 70, as described above for otherembodiments.

In another embodiment, an arterial balloon cannula with associatedfilter and distal flow diffuser is provided as depicted in FIGS. 12 and12a. In this embodiment the distal end of the cannula 10, is closed witha cap 500 and the flow diffuser is a rounded cone 502 extending insidethe lumen of the cannula. As shown in FIG. 12, the cap preferably has arounded, hemispherical shape to facilitate the insertion of the distalend of the cannula into the vessel. The flow diffuser tapers towards theproximal end of the cannula 10 starting from the end cap. The shape ofthe flow diffuser is preferably conical in order to avoid damaging theblood. However, other shapes, including pyramidal shapes, may beemployed.

As shown in FIG. 12a, a plurality of outlet openings 504 are formed inthe sidewall of the cannula 10 adjacent to its distal end. The openingsmay have an arched configuration, with the curved portion 506 of eacharch oriented in the upstream direction. Although any number of openingsare possible, a preferred embodiment has six openings. Preferably thetotal area of the openings is greater than the area of the distal endopening of a conventional catheter of the same diameter. The length ofthe openings 504 are also preferably greater than the length of the flowdiffuser 502.

In another embodiment, an arterial balloon cannula with filtration meansis provided as depicted in FIGS. 13 and 13a. In this embodiment, thedistal end of the cannula 10 contains a diffuser 602 with a helicalconfiguration. The diffuser 602 can be held in place within the cannulaby the tapering configuration of the distal end of the cannula, byadhesives, by ultrasonic welding, or by some other suitable means. Thediffuser is preferably formed from a flat rectangular member with asingle one-hundred-eighty degree twist. In this embodiment, the distalend of the cannula is partially blocked. Additionally, any number ofoutlet opening 604 may be formed in the sidewall of the cannula.

The intra-cannula flow diffusers of FIG. 12 and FIG. 13 may also beemployed proximal to the filter by positioning the diffuser within thearterial balloon cannula of FIG. 7. Other variations and details ofintra-lumen flow diffusers may be found in Cosgrove et. al., LowVelocity Aortic Cannula, U.S. Pat. No. 5,354,288, which is incorporatedby reference herein.

In another embodiment, an arterial balloon cannula is provided as inFIG. 14. In this embodiment the proximal end of a flow diffuser 702 isconnected to the distal end of the cannula 10 by a plurality ofstructural supports 704. The diffuser 702 is preferably conical,although other shapes may be used. The distal end of the flow diffuser702 extends to the apex of the filter 706 by virtue of a linear shaft708 said shaft running through the center of the expanded filter. Inthis embodiment the flow diffuser 702 diffuses blood flow proximal tothe filter 706.

In another embodiment, an arterial balloon cannula is provided as inFIG. 15. In this embodiment the flow diffuser 802 is contained withinthe distal end of the blood cannula 10. In a preferred embodiment, thediffuser 802 is the helical diffuser shown in FIG. 13 and 13a. The flowdiffuser 802 can be held in place by the tapering configuration of thedistal end of the cannula, by adhesives, by ultrasonic welding, or bysome other suitable means. Unlike the invention of FIG. 13, the distalend of the diffuser 802 is attached to the apex of the filter 806 byvirtue of a linear shaft 808 said shaft running through the center ofthe expanded filter. The shaft may be any shape which will nottraumatize blood components, and preferably comprises a rounded surfacewhich tapers outward in the distal direction. In this embodiment theflow diffuser diffuses cannula blood flow proximal to the filter. Thecannula 10 optionally contains openings 803 in its distal end 804 tofurther diffuse the cannula blood. In an alternate embodiment, blooddiffuser 802 is contained within cannula 10 but is not connected tofilter 806 said filter being supported as disclosed in FIG. 7.

Although cannulas have been selected for purposes of example, theinventions of FIGS. 12-15 can be readily applied for use in arterialballoon catheters.

It is to be understood that flow diffusers such as those of FIGS. 12-15can be used in any blood filter device having a blood supply cannula andassociated filter, including the devices depicted in FIG. 3 and FIG. 4.Furthermore, the diffuser of FIG. 15 may be employed inside a cannulahaving a distal filter, such as in FIG. 7, thus creating a blood filterdevice with two filters, one proximal to and one distal to the cannulaopening.

In an alternative embodiment, shown in FIG. 16, an arterial ballooncannula and associated filter 906 include a generally cylindrical filtersleeve 908 disposed circumferentially about the distal end of thecannula and attached to four control lines 902a, 902b, 904a, 904b.Proximal force on unroll control lines 904a and 904b unrolls filtersleeve 908 from its depicted position so as to capture the filterresulting in the position shown in FIG. 17. In this embodiment, themanner of unrolling the filter sleeve is analogous to the unrolling of alatex condom. Although the sleeve may be any shape, provided it bothencases the cannula and rolls up in response to the control lines, in apreferred embodiment the sleeve has a circular cross-section.

In FIG. 16 the filter sleeve 908 is rolled back distal to the filter, toallow the filter to be fully expanded. FIG. 16 shows a cross-sectionalcut-away of the sleeve. The full sleeve, not depicted, is a continuouspiece surrounding the cannula about a 360 degree radius. In a preferredembodiment, a circular condom-like sleeve is attached at theouter-diameter of the cannula along the arc of circle 910. Thecondom-like sleeve has a distal opening to permit exit of the cannulatip. In a preferred embodiment a pair of control lines 902a and 904aenter a control lumen at points 928 and 929 respectively and run insidecontrol lumen 922 adjacent the cannula lumen until exiting the controllumen at a proximal point on the cannula (not shown). In the preferredembodiment, a second set of control lines 902b and 904b enter a secondcontrol lumen 924 at points 926 and 927 respectively, said pointslocated one-hundred eighty degrees from the first lumen along thecannula's outer diameter.

As shown in FIG. 17, unroll control lines 904a and 904b are attached tosleeve 908 at points 914 and 916 said points located on the proximal endof the unrolled sleeve. Consequently, when sleeve 908 is rolled-up asshown in FIG. 16, points 914 and 916 are rolled into the center of thenautilus-shaped lip of sleeve 908 while unroll control lines 904a and904b are rolled-up alongside the sleeve.

In contrast, roll-up control lines 902a and 902b are attached to thecannula at points 918 and 920, respectively. Both points 918 and 920 arelocated on arc 910. When the sleeve is rolled-up, as shown in FIG. 16,the roll-up control lines 902a and 902b run from their respective pointsof attachment 918 and 920, along the exposed side of the rolled-upsleeve, and enter the control lumens 922 and 924 at points 926 and 928respectively. After entering the control lumens, the roll-up linesproceed through the control lumens until exiting at points (not shown)proximally located on the cannula.

FIG. 17 shows the same arterial balloon catheter and associated filteras FIG. 16 but with the sleeve 908 fully unrolled and capturing filter906. The unrolled sleeve provides a compact, smooth profile for thedevice's introduction to and retraction from a vessel. In order tounroll the sleeve from the FIG. 16 position, the unroll lines 904a and904b of FIG. 17 have been pulled in a proximal direction, away from thecannula tip. Consequently, points 914 and 916 are positioned at theproximal end of unrolled sleeve 908.

When the sleeve is in the unrolled state, the roll-up control lines 902aand 902b run from points 918 and 920 respectively, along the undersideof the sleeve 908, around the proximal end of the sleeve, and thendistally along the outer side of the sleeve before entering the controllumens 922 and 924 at points 926 and 928 respectively. After entering atpoints 926 and 928, the roll-up control lines 902a and 902b travelthrough the control lumens until exiting the control lumens at points(not shown) located at the proximal region of the cannula. When thesleeve is in the unrolled position as shown in FIG. 17, the roll-uplines may be pulled in a proximal direction, away from the cannula tip.Pulling the roll-up lines causes sleeve 908 to roll-up until reachingthe rolled-up state shown in FIG. 16. In a preferred method of use, thesleeve 908 is unrolled prior to insertion of the cannula in a vessel,rolled up during mesh deployment and once again unrolled prior tocannula retraction.

FIG. 18 shows a cross-sectional detail of the sleeve 908 in the unrolledstate, with emphasis on the points of attachment for the control lines.In the FIG. 18 embodiment, the sleeve, which is a continuous about 360degrees (not shown), is directly connected to the two roll-up lines 902aand 902b at points 918 and 920 respectively. Alternatively, the roll-uplines are attached directly to the cannula at points neighboring 918 and920 located immediately distal to the distal end of the sleeve. Pullingthe roll-up lines 902a and 902b in a proximal direction, as shown by thearrows in FIG. 18, causes the sleeve to roll-up like a condom.Accordingly, the sleeve material should be thin enough to avoid bunchingand to provide smooth rolling in reaction to the proximal force exertedby the roll-up lines. In a preferred embodiment, the sleeve is made oflatex, with a thickness of between 3 and 14 thousandths of an inch. In amore preferred embodiment, the sleeve is made of latex with a thicknessof between 4 and 16 thousandths of an inch. The invention may also usesilicone or another silastic, biocompatible material to construct thesleeve. Other materials as are known in the art may permit use of asleeve with less than 4 thousandths of an inch provided the materialgives suitable assurances against breaking or tearing.

FIG. 19 is a three-dimensional depiction of the cannula 10, filter 906and sleeve 908, with sleeve 908 in the rolled-up state. In oneembodiment the filter 906 is located distal to the cannula opening suchthat cannula output is filtered upon leaving the cannula. In anotherembodiment, the filter is located proximal to the cannula opening suchthat cannula output is downstream of the filter. The cannula opening mayoptionally have a planar diffuser 932. Filter 906 is made of mesh whichis contiguous with a sealing skirt 930. With the exception of entrancepoint 933, both the roll-up and unroll lines enter and exit the cannulaat points not shown. In a preferred embodiment, the control lines attachto a control line actuating mechanism such as a capstan, ring or pulley(also not shown). In this embodiment, the structure adapted to open andclose the filter may be an umbrella frame (not shown), such as depictedin FIG. 10, or alternatively an inflation balloon (not shown), such asshown in FIG. 7 and FIG. 9. The FIG. 19 embodiment may be used with anyof the various means to actuate the structure as described herein.Pulling the unroll control lines 904a and 904b in a proximal directioncauses the capture sleeve to roll out over the top of the filter.Subsequently pulling the roll-up control lines 902a and 902b rolls-upthe captured sleeve thereby permitting filter deployment. In FIG. 19 theunroll lines are oriented at an angle of 180 degrees from one anotheralong the circumference of the filter (thus 904b is not shown). Theroll-up lines 902a and 902b are similarly oriented at an angle of 180degrees from one another. However, as with the inventions of FIGS.16-18, this embodiment may employ any number of control lines spaced atvarying distances around the outer diameter of the filter sleeve.Cannula 10 is shown in use in FIG. 19A. Balloon occluder 65 expands toengage the lumen of aorta 99. FIG. 19A also shows an expansion framecomprising an umbrella having a plurality of primary struts 511 and aplurality of secondary struts 512 which are connected to the primarystruts at about the midpoint of the primary struts.

FIG. 20 shows an alternative embodiment wherein one control ring 936controls rolling and unrolling of the sleeve 934 with the assistance ofa pulley mechanism. The control ring 936 is movable in both the proximaland distal directions along the outer diameter of the cannula (notshown). Control ring 936 is directly attached to unroll control lines904a and 904b and attached to roll-up control lines 902a and 902bthrough pulley 934. Proximal movement of the control ring causes thesleeve 908 to unroll. Distal movement conversely causes sleeve 908 toroll up.

In another embodiment of an arterial balloon cannula, shown in FIG. 21,the cannula contains a collapsible section such that it can accommodatethe filter seal 907 and the filter 906 and any other components of thefiltration means. The collapsible section 938 is made out of anelastomeric material, such as latex. In another embodiment thecollapsible section is a double walled balloon. In a preferredembodiment the section is made of a flexible material with built inmemory such that the collapsible walls automatically return to theirnon-collapsed state when deployment force expands the filter. Thecollapsing section 938 begins just proximal to the site of the filterseal 907 when the filter is in the collapsed state. In the embodimentshown, the collapsing section has a length equal to the length of thefilter 906 and filter seal 907. In an alternative embodiment, thecollapsing section extends to the tip of the catheter from just proximalto the filter seal. The deformable section collapses radially inwardwhen the filtration assembly is closed in order to produce a low-profiledistal end to the cannula. Thus, a portion of the radial volume of thecannula is occupied by the filtration assembly when the filtrationassembly is deployed; however, the blood flowing through the cannulasubsequently blows the deformable cannula walls outwards to allow theflow of blood through the entire cannula diameter. It is to beunderstood this embodiment may be used in combination with the sleeveembodiments previously shown herein.

In another embodiment of an arterial balloon cannula, with associatedfilter shown in FIGS. 22 and 23, the blood cannula 10 is composed of amedically acceptable elastic material, such as latex, silicone, rubber,and the like. As shown in FIG. 23, the blood cannula has an intrinsiclength and diameter which characterizes the cannula when it is not underaxial stress. The intrinsic length and diameter of the cannula variesaccording to vessel size. The cannula may be closed with a cap diffuserof the type disclosed in FIG. 12. Alternatively, the cannula may be onlypartially closed at the tip as in FIG. 13. As shown in FIG. 22, a stylet944 is placed in the cannula 10 and engages the cannula tip. In analternative embodiment, the stylet engages a ring suspended at theopening of an open tip. When inserted fully into the cannula, thelengthy stylet 944 engages the distal tip of the elastic cannula andaxially stretches the cannula body. In this way the cannula is stretchedso as to reduce cannula diameter upon introduction into the vessel. Afinger grip 946 secured to the proximal end of the stylet includes latchmember 948. The latch member engages a recess 950, formed on a proximalfitting 952 of the cannula, in order to maintain the cannula's stretchedconfiguration. After insertion in the vessel, the elastic cannula isradially expanded and shortened by depressing latch member 948 andwithdrawing the stylet as in FIG. 23.

In this embodiment, the filter 908 is fixed to the outer diameter of theunexpanded elastic cannula by tether lines 954 and 956 such that, whenthe stylet is introduced, cannula expansion causes the tether lines togo taut, which in turn contours the filter to the cannula. Consequently,as shown in FIG. 23, when the stylet is withdrawn, the cannula shortensthereby permitting expansion of the filter. Although various biasing andfilter opening mechanisms may be used, in one preferred embodiment, thefilter itself is made of memory-wire biased to an open state.

In another embodiment shown in FIGS. 24 and 25, the distal cannulaportion 960 upon which the filter assembly 962 is mounted is, at leastin part, a radially flexible material or composite construction which isnormally in a necked down, contracted position. This allows thecontracted filter assembly 962 to create as small of a profile aspossible for insertion into the blood vessel. The necked-down portion964 of the distal cannula is opened by inserting a close fittingexpander 966 through the necked-down portion. The expander 966 has adistal end 967. As a result of the expander insertion, the filterassembly 962 exhibits an extruding profile relative to the outercontours of the distal cannula. Optionally as shown in FIG. 24, thefilter assembly 962 may be fully deployed by a deployment mechanism (notshown), as previously described herein. In both FIGS. 24 and 25, theexpander is fixed relative to the proximal cannula 968. Both are moveddistally relative to the distal cannula so as to insert the expanderinto the collapsible section. Alternatively, the expander 966 may moveindependent of the proximal cannula 968.

In another embodiment shown is FIGS. 26 and 26A to 26D, cannula 350includes filter 906 having skirt 970 disposed around its outermost edge.Skirt 970 is an elastomeric strip of material (e.g., silicon or othersuitable material) attached to the proximal edge of the filter mesh.Skirt 970 forms a compliant edge which conforms to vessel lumentopography and gives a better seal with the vessel lumen when the filteris deployed. Moreover, the compliant edge 970 allows for changes in thevessel interior dimension as the vessel pulses from systole to diastole.Both unroll control lines 904a and 904b, as well as roll-up controllines 902a and 902b (not shown) are routed through tube 978 and thenthrough the cannula housing at location 971 and thereafter ride withintubing 972 to the point where they are manipulated outside of the body.In addition to the roll-up and unroll control lines, a fifth controlline is also carried through tube 972 and location 971 for the purposeof operating the umbrella frame 973 depicted in FIG. 26. This controlline can ride either inside or outside of tube 978. The umbrella frameconsists of a series of primary struts 974 extending from the distal toproximal end of the mesh and disposed circumferentially thereabout, anda series of secondary struts 975. Struts 975 connect at their proximalend to struts 974 and at their distal end are slidably connected to theaxis of the conical filtration mesh. Secondary struts 975 thereforeoperate to open and close the expansion frame between a radiallyexpanded and radially contracted condition.

In another embodiment shown in FIG. 27, cannula 350 includes on itsdistal end a "windsock" or open-ended sleeve 976 which is either aporous mesh, a non-porous material (e.g., silicon), or a non-porousmaterial with holes which allow some degree of lateral blood flow. InFIG. 27, the windsock cannula is shown deployed within aorta 99. As canbe seen, embolic debris dislodged upstream of the cannula will becarried through the windsock 976 and will exit the distal opening 977.Sleeve 976 thereby prevents passage of embolic material laterally in theregion of the carotid arteries and thereby prevents or reduces theoccurrence of embolic material reaching the brain. At the same time,however, the windsock apparatus overcomes difficulties associated withfilter blockage due to blood clotting and buildup of debris bydelivering a high volume of blood downstream of the carotid arterieswithout the need to pass laterally through the sleeve.

It is to be understood that the cannula devices of FIG. 16-FIG. 27 mayoptionally employ a balloon occluder proximal to the filter, asdisclosed in FIG. 1-FIG. 10.

In another embodiment of an arterial balloon cannula, as shown in FIG.28, a filter and balloon occluder are integrated as one piece 987 anddisposed concentrically about the cannula, 10. As a result, the cannulaemploys a single inflation port 988 for both occlusion of the vessel anddeployment of the filter. In a preferred embodiment, a slide 990 is usedto collapse the filter-balloon unit via control lines (not shown) whenpassage of the device through the vessel is required.

In another embodiment of an arterial balloon cannula, as shown in FIG.29, a cannula contains an opening 992 proximal to the balloon occluder65 and filter 75. The opening is linked by a conduit 991 which runsalong the inside of the cannula and is isolated from the cannula bloodflow. In a preferred embodiment the conduit carries a source ofmyocardial prevention solution, such as a cardioplegia solution, whichis pumped into the heart side of the balloon-occluded aorta.Alternatively, the conduit may pump saline solution or a solution whichfacilitates pressure monitoring via the conduit. The construction andoperation of the valve system to accommodate cardioplegia output on aperfusion cannula is explained in detail in Hill, U.S. Pat. Nos.5,522,838, 5,330,498 (see FIG. 6), and 5,499,996, incorporated herein byreference.

In an arterial balloon catheter embodiment, as shown in FIG. 30, acatheter similar to the catheter in FIG. 12 includes openings 992located proximal to the balloon so as to deliver oxygenated blood to thearterial side of the balloon occluder. Additionally, the arterialballoon catheter contains a fluid-isolated second lumen 996 and opening998 at the distal end of the catheter 100 for delivery of cardioplegiasolutions to the heart side of the balloon occluder 65.

In another embodiment, a device for occluding arterial vessels isprovided by a cannula having a dam or other impermeable structure asshown in FIG. 31. Cannula 50 is equipped with mechanical dam structure513 at the distal end of the cannula, dam 513 having a plurality oflifting arms 551. The dam may optionally include a balloon seal 514disposed circumferentially and continuously about 513. Balloon 514 maybe filled with saline, self-expanding foam, or a combination of both.Dam 513 is constructed of any nonpermeable material, examples of whichinclude silicon, urethan, or other occlusive barriers.

A balloon occluder on a catheter in accordance with another embodimentis depicted in FIGS. 32 and 32A. Referring to FIG. 32, catheter 515includes balloon occluder 65 disposed about the distal region thereof.The catheter may be used as a standalone device or with a blood cannula.Cannula 515 includes an inflation lumen for inflating balloon 65, andmay optionally include a second lumen for delivery of fluids, such ascardioplegic solution. In use, the device is deployed as shown in FIG.32A. Catheter 515 may be deployed through cannula 50 and enter the aortaupstream of cannula 50. Catheter 515 may optionally further includefilter 75. In another embodiment, catheter 515 is delivered throughcardioplegic cannula 516. In this embodiment, catheter 515 includessecond inner lumen 517 for delivery of cardioplegia solution to theheart. Thus, the occlusion catheter can be delivered either through anadditional lumen on perfusion cannula 50 or through an entirely separatecardioplegic cannula 516 which is inserted through the aorta upstream ofthe entry point 450.

A cannula with a self-inflating balloon is shown in FIGS. 33 and 33A.Cannula 50 includes balloon occluder 65 disposed about a distal regionthereof. The balloon is loaded with foam which is biased to expandradially outwardly. Vacuum is applied to the balloon inflation lumen toradially collapse the balloon occluder 65 and thereby compress foam 518.When the cannula is in place within the aorta, the vacuum is released,and balloon occluder 65 expands radially outwardly. FIG. 33A shows aself-expanding balloon occluder wherein cannula 50 includes rigidsection 524 and deformable section 523 which, upon balloon compression,collapses inwardly to economize on the cross-sectional area of thedevice.

An adhesive coated balloon cannula is shown in FIG. 34. Cannula 50includes balloon occluder 65 at a distal region thereof. Balloon 65 isequipped with adhesive coating 519 on an outer radial surface thereof.Adhesive 519 functions to grab and retain any embolic material dislodgedfrom the vessel wall during a procedure.

An expandable wire occluder is shown in FIGS. 35 and 35A. Wire 520 ispreformed into a shape about the distal end of the cannula so that itwill expand radially outwardly when longitudinally compressed. Thedevice further includes pulling member 521 which is connected to thedistal end of wire 520. When pulled, member 521 causes expanding wire520 to expand radially outwardly as shown in FIG. 35A. The expandingwire 520 may optionally be further equipped with an impermeable elasticcoating 522.

A cannula introducer is shown in FIG. 36. Cannula 50 includes bypassoutput port 525 in one radial position, and passage 526 in anotherradial position, preferably 180° apart. Passage 526 is adapted toreceive a balloon catheter 515 having balloon occluder 65 on a distalend thereof. This modular design allows the balloon catheter 515 to beinserted and deployed and retracted independently of the cannula.

An integrated occlusion cape cannula is shown in FIG. 37. Cannula 50includes bypass output port 525 at a first radial position, andocclusion cape 528 at a second radial position, preferably substantially180° from bypass output port. Also included on the distal end of cannula50 are mesh 75 and mechanical support structure 527. Mesh filter 75 ispreferably equipped with an elastomeric skirt disposed circumferentiallyabout the outer diameter of the mechanical support structure. Thesupport structure is typically outside of mesh 75. Cape 528, oncedeployed, covers and lines mesh filter 75 thereby blocking passage offluids. Cape 528, once retracted, is detached and withdrawn into a portin cannula 50 for removal from the aorta. The cape can be inverted toblock fluid flow in the opposite direction.

The use of a balloon occluder catheter in conjunction with acardioplegic catheter is depicted in FIG. 38. Bypass cannula 50 isinserted downstream of cardioplegic cannula 520. Balloon occluder 65 isdisposed on a catheter 553 which is insertable through lumen 530 oncardioplegic cannula 529. Cannula 529 is equipped with cardioplegiasolution exit port 531 and optionally having diffuser ports 552.Catheter 553 may optionally include solution ports 532. The advantage ofsuch a system over a cannula-based balloon occluder is that the occluderis independent of the bypass cannula. Therefore, this design iscompatible with any bypass cannula design. Moreover, the bypass cannulais available for placement anywhere distal of the occluder.

An aortic occluder with modular design is shown in FIG. 39. Cannula 50includes occluder guide 534 at a distal end thereof. Guide 534 comprisesa lumen adapted to receive balloon occluder device 533. Occluder 533includes balloon 65 and fluid port 535 as a conduit for cardioplegicsolution. Guide 534 is advantageous in that it directs or positions theoccluder at a desired location rather than allowing the occluder torandomly position itself.

Human anatomy including the rib cage with deployed occluder is depictedin FIG. 40. Occluder cannula 50 is disposed through access port 538 andthereafter enters the aorta behind sternum 554. The rib cage is depictedgenerally by numeral 537. Occluder 536 is shown deployed within aorta99. The concept of port access allows a surgeon to enter the aorta via aport for a minimally invasive approach. By accessing the aorta directly,the device is deployed without the need for visual guidance, e.g.,fluoroscopy, echocardiography. This device would obviate the need for asternotomy procedure which is generally associated with conventionalcoronary artery bypass grafting surgery. In use, the aortic occluderpasses through the access port to the aorta. Once positioned on theaorta, the occluder device is inserted into the vessel and the occluderis deployed. The occlusion device may comprise a single one-pieceoccluder cannula or multiple components. One simple design would utilizean inflation balloon on the end of a cannula. The shaft of the cannulacould be flexible or stiff depending on whether the surgeon prefers todirect the occluder using a clamp or trocar or prefers a more steerableunit. The cannula may include one or more lumens for inflation and fluidpassage.

A single-piece occluder is shown in FIG. 41. Occluder cannula 50includes occlusion balloon 65 disposed on its distal end. Cannula 50 isequipped with infusion ports 540 for passage of any appropriate fluid,e.g., cardioplegic solution. Cannula 50 optionally includes seatingbumps 539 for additional sealing with the interior of the aorta. TheL-shaped cannula may be preformed or flexible to allow forself-centering.

An alternate design for a single-piece occluder is depicted in FIG. 42.Cannula 50 assumes a J-shape, and includes occlusion balloon 65 on adistal end thereof. Infusion port 541 allows passage of appropriatesolution to the heart, e.g., cardioplegic solution. These singlecomponent occluders as shown in FIGS. 41 and 42 may be inserted througha pre-slit section of the aorta, or a trocar may be advanced through alumen, and extended beyond the cannula tip. The trocar would be used topierce the aorta wall. Once the trocar is in the vessel, the occluder isadvanced and then the trocar removed.

A multiple component port access aortic occluder is depicted in FIG. 43.The system includes trocar 555 having preshaped configuration 542, sharptip 544, and position limiters 543. Cannula 50 includes suture plate548, kink resistant shaft 547, infusion port 545, and hemostasis valve546. Occlusion catheter 556 includes balloon occluder 565, inflationport 549, and infusion lumen 550. Occluder 556 is shaped to receivefilter mesh 75. Cannula 50 is adapted to receive trocar 555 through theinfusion port 545, and to receive catheter 556 through hemostasis valve546. In use, a port access point or window is opened on the patient'schest. Tissue from the port to the aorta is dissected. The trocar andcannula are advanced to the aortic wall. A purse string suture(s) may berequired to aid in wound closure and to secure the device. At thedesired location, the trocar is advanced through the aortic wall and thecannula is pushed with the trocar. Once in the vessel, the cannula issecured and the trocar is removed. At this point, the occluder (andfilter) may be advanced and deployed. Cardioplegia or other fluid maythen be circulated through the infusion lumens.

An aortic balloon cannula is depicted in FIG. 44. Cannula 50 is insertedthrough aorta 99 and includes balloon 65 inflated to occlude the flow ofblood in the aorta. The lumen of bypass cannula 50 releases oxygenatedblood downstream of occluder 65. In another embodiment, a ballooncatheter is used for occlusion as shown in FIG. 45. Cardioplegia cannula529 penetrates aorta 99 and allows deployment of balloon catheter 557through cannula 529. Catheter 557 includes occlusion balloon 65 on adistal region thereof. Catheter 557 is deployed through a lumen ofcardioplegia cannula 529, wherein the lumen is optionally the same or adifferent lumen than the lumen which carries cardioplegia solution. Inanother embodiment, a cardioplegia balloon cannula is provided asdepicted in FIG. 46. Cannula 529 includes balloon 65 mounted on a distalregion thereof which is expandable within aorta 99 to occlude blood flowtherein. Cannula 529 further includes distal port 558 for delivery ofcardioplegia solution to the heart.

In use, the arterial balloon catheter is deployed through the femoralartery while maintaining peripheral cardiopulmonary bypass as describedin Peters, U.S. Pat. No. 5,433,700, Machold et al., U.S. Pat. No.5,458,574, Stevens, International Application No. PCT/US93/12323, andSteven et al., International Application No. PCT/US94/12986. Thus, thecatheters of FIG. 12 and FIG. 30 may be used to induce cardioplegicarrest of a heart by the steps of maintaining systemic circulation withperipheral cardiopulmonary bypass, occluding the ascending aorta throughpercutaneous use of the arterial balloon catheter, introducing acardioplegic agent into the coronary circulation, and venting the leftside of the heart as discussed in the above-identified patents andapplications. Moreover, the arterial balloon catheter can be used duringopen heart surgery or for any of a number of other procedures known inthe art which involve the heart, aorta, or vasculature. Peripheralcardiopulmonary bypass is connected to a major vein, e.g., the femoralvein to withdraw blood, remove carbon dioxide, oxygenate the withdrawnblood, and return the oxygenated blood to the patient's arterial systemthrough a major artery, e.g., the femoral artery. The catheters of FIG.12 and FIG. 30 may be introduced by subclavian delivery and inducecardioplegic arrest of the heart as disclosed in Sweezer, U.S. Pat. No.5,478,309, herein incorporated by reference.

As a purely illustrative example of one of the methods of filteringblood as disclosed herein, the method will be described in the contextof cardiac bypass surgery as described in Manual of Cardiac Surgery, 2d.Ed., by Bradley J. Harlan, Albert Sparr, Frederick Harwin, which isincorporated herein by reference in its entirety.

A preferred method of the present invention may be used to protect apatient from embolization during cardiac surgery, particularly cardiacbypass surgery. This method includes the following steps: introducing amesh into an aorta of the patient; positioning the mesh to coversubstantially all of the cross-sectional area of the aorta so that themesh may capture embolic matter or foreign matter in the blood;adjusting the mesh to maintain its position covering substantially allof the cross-sectional area of the aorta; and removing the mesh and thecaptured foreign matter from the aorta. A variant comprises placing acylindric mesh at the level of the take off of the cerebral vessel todivert emboli otherwise destined for the brain to other parts of thebody.

During the cardiac surgery, the aorta is either clamped a number oftimes or occluded with a balloon occluder as disclosed herein. Becauseballoon occlusion and/or clamping the aorta dislodges atheromatousmaterial from the walls of the aorta, which is released into thebloodstream, the mesh must be positioned within the aorta beforeclamping or balloon occlusion begins. Atheromatous material alsoaccumulates behind the balloon occluder and/or clamps during the surgeryand, because removal of the clamps and/or deflation of the balloonoccluder releases this material into the bloodstream, the mesh must bemaintained within the blood stream for about four to ten minutes afterdeflation of the occluder and/or removal of the clamps. Because theaorta is often a source of much of the atheromatous material that iseventually released into the bloodstream, it is preferable to place themesh in the aorta between the heart and the carotid arteries. Thisplacement ensures that foreign matter will be captured before it canreach the brain.

For illustration purposes, the method for balloon occlusion andfiltering blood will be described in connection with the device depictedin FIGS. 4 and 5. After a patient has been anaesthetized and thepatient's chest has been opened in preparation for the bypass surgery,the cannula 10, ranging from about 22 to about 25 Fr. O.D. in size, isintroduced into an incision made in the aorta. The cannula 10 is suturedto the aortic wall, and the heart is paralyzed. The balloon aorticcannula is stored in a closed position, in which the balloon occluder 65is deflated and folded in upon itself, and the mesh 75 is closed. Thecannula 10 and its associated structures will not interfere with otherequipment used in the surgical procedure.

Saline is introduced into the inflation seal 70 through the actuationassembly (not shown) from an extracorporeal reservoir, and the inflationseal gradually assumes an open position in which the balloon 70 isinflated in a donut-shape and the mesh 75 is opened to coversubstantially all of the cross-sectional area of the vessel. In theopened position, the mesh is ready to capture foreign matter in theblood flow. By adjusting the amount of saline introduced into theballoon 70, the surgeon may control the amount of inflation andconsequently the degree to which the mesh 75 is opened. Saline is thenintroduced into balloon occluder 65 under pressure through lumen 60, andfrom an extracorporeal reservoir, and the balloon occluder graduallyassumes an open position (see FIG. 5) in which the balloon is opened tocover substantially all of the cross-sectional area of the vessel. Incertain embodiments, the surgeon will dissect around the circumferenceof the aorta, and a cuff will be installed around the area of balloonocclusion to hold the aorta firmly against the balloon occluder. Afterthe balloon aortic cannula has been thus actuated, blood from a bypassmachine is introduced into the aorta through the cannula 10.

It will be understood that balloon occlusion is used to block the flowof blood back into the heart. Balloon occlusion may dislodgeatheromatous material from the walls of the aorta and releases it intothe blood flow. Because balloon occlusion is performed upstream from thefilter 75, the atheromatous material will be filtered from the blood bymesh 75. While the aorta is occluded, the surgeon grafts one end of avein removed from the patient's leg on to the coronary artery. Inanother embodiment, arterial grafting, such as internal mammary arterygrafting, may be employed. After the surgeon checks the blood flow tomake sure there is no leakage, the balloon occluder is deflated.Atheromatous material accumulates behind the balloon occluder and, whenit is deflated, this material is released into the blood flow, whichwill be filtered by mesh 75. The flow rate from the bypass machine iskept low to minimize embolization, and the heart is made to beat again.

During surgery, the position of the mesh may require adjustment tomaintain its coverage of substantially all of the cross-sectional areaof the aorta. To accomplish this, the surgeon occasionally palpates theoutside of the aorta gently in order to adjust cannula 10 so that themesh 75 covers substantially all of the cross-sectional area of theaorta. The surgeon may also adjust the location of cannula 10 within theaorta.

The balloon aortic cannula may also be used in conjunction with TCDvisualization techniques. Through this technique, the surgeon mayactuate the inflation seal and mesh only when the surgeon expects aflurry of emboli such as during aortic cannulation, inception, andtermination of bypass, balloon occlusion, deflation of an occlusiveballoon, aortic clamping, and clamp release.

The surgeon then occludes and/or clamps the aorta longitudinally topartially close the aorta, again releasing the atheromatous material tobe filtered by the mesh. Holes are punched into the closed off portionof the aorta, and the other end of the vein graft is sewn onto the aortawhere the holes have been punched. The balloon occluder is deflatedand/or the aortic clamps are removed, again releasing accumulatedatheromatous material to be filtered from the blood by the mesh. Thesurgeon checks the blood flow to make sure there is no leakage. Theheart resumes all the pumping, and the bypass machine is turned off,marking the end of the procedure.

The saline is then removed from the balloon occluder and the inflationseal via the actuation assembly, deflating the balloon occluder,inflation seal, and closing the mesh around the captured emboli.Finally, the balloon aortic cannula, along with the captured emboli, areremoved from the body. Because the balloon aortic cannula is in placethroughout the procedure, any material released during the procedurewill be captured by mesh 75.

When the balloon arterial cannula is used in conjunction with otherinvasive procedures, the dimensions of the device should be adjusted tofit the vessel affected. An appropriate mesh also should be chosen forblood flow in that vessel. In use, the device may be positioned so thatit is placed downstream of the portion of the vessel that is affectedduring the procedure, by occlusion and/or clamping or other step in theprocedure. For example, in order to capture emboli material in a legartery, the cone-shaped filter can be placed such that the cone pointstoward the foot.

An advantage of the devices and methods of the present invention and themethods for filtering blood described herein is that it is possible tocapture foreign matter resulting from the incisions through which thedevices are inserted. Another advantage of the devices of the presentinvention is that the flexibility of the inflatable balloon allows it toconform to possible irregularities in the wall of a vessel.

While particular devices and methods have been described for filteringblood, once this description is known, it will be apparent to those ofordinary skill in the art that other embodiments and alternative stepsare also possible without departing from the spirit and scope of theinvention. Moreover, it will be apparent that certain features of eachembodiment, as well as features disclosed in each reference incorporatedherein, can be used in combination with devices illustrated in otherembodiments. Accordingly, the above description should be construed asillustrative, and not in a limiting sense, the scope of the inventionbeing defined by the following claims.

What is claimed is:
 1. A method for occluding an aorta forcardiopulmonary bypass, comprising the steps of:providing a cannulahaving a proximal end, a proximal port, a distal region, and a lumenwhich extends distally from the proximal end and terminates andcommunicates with an infusion port in the distal region; providing anocclusion catheter having a proximal end, a distal end, and an occludermounted on the distal end of the catheter; making an incision in theaorta; inserting the cannula through the incision into the aorta;inserting the occlusion catheter through the proximal port andpositioning the occluder in the aorta; expanding the occluder; andinfusing oxygenated blood through the proximal end of the cannula,through the infusion port, and into the aorta.
 2. The method of claim 1,wherein the occluder is a balloon occluder, and wherein the step ofexpanding the occluder includes inflating the balloon.
 3. The method ofclaim 2, wherein the catheter further comprises an inflation lumen whichcommunicates with the balloon occluder.
 4. The method of claim 1,wherein the catheter further comprises a lumen communicating with a portdistal the occluder, and wherein the method further comprises the stepof delivering cardioplegia to the heart.
 5. The method of claim 1,wherein the occlusion catheter is inserted through the proximal portafter the step of inserting the cannula into the aorta.
 6. The method ofclaim 1, further comprising the step of performing a surgical procedureon at least one of the heart, aorta upstream of the occluder, andvasculature associated with the heart and/or aorta.